1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8"/>
<meta http-equiv="Content-Style-Type" content="text/css"/>
<title>
The Project Gutenberg eBook of A Bacteriological Study of Ham Souring, by C. N. Mcbryde, M. D..
</title>
<link rel="coverpage" href="images/i_cover.jpg"/>
<style type="text/css">
body {
margin-left: 10%;
margin-right: 10%;
}
h1
{
margin-top: 2em; margin-bottom: 2em;
text-align: center;
font-size: x-large;
font-weight: normal;
line-height: 1.6;
}
h2,h3,h4,h5, h6{
text-align: center;
clear: both;
}
h5 {font-size: 1.3em; font-weight: bold;}
h6 {font-size: 1.1em;}
.half-title {
margin-top: 2em; margin-bottom: 2em;
text-align: center;
font-size: x-large;
font-weight: normal;
line-height: 1.6;
}
div.chapter {page-break-before: always;}
h2.nobreak {page-break-before: avoid;}
/* Paragraphs */
p {text-indent: 1em;
margin-top:.75em;
text-align: justify;
margin-bottom:.75em;
}
.psig {text-align: right; margin-right: 2em;}
.pnb {margin-bottom: 0em;}
.hang {text-align: justify; padding-left: 1.75em; text-indent:-1.75em;}
hr.chap {width: 65%; margin-left: 17.5%; margin-right: 17.5%;}
hr.small {width: 25%; margin-left: 37.5%; margin-right: 37.5%;}
@media print { hr.chap {display: none; visibility: hidden;}}
ul {font-size:.9em; list-style-type: none;}
table {
margin-left: auto;
margin-right: auto;
}
.brdr {border: 1px solid black; border-collapse: collapse;
font-size:.9em;}
.brdr th {border: 1px solid black;}
.standard { font-size:.9em; border-collapse: collapse;}
td, th {padding: 3px;}
.tdh {text-align: justify; padding-left: 1.75em; text-indent:-1.75em;}
.tdl {text-align: left;}
.tdli1 {text-align: left; padding-left: 2em;}
.tdli2 {text-align: left; padding-left: 4em;}
.tdli3 {text-align: left; padding-left: 6em;}
.tdr {text-align: right;}
.tdc {text-align: center;}
.tdct {text-align: center; vertical-align: top;}
.tdrt {text-align: right; vertical-align: top;}
.tdrb {text-align: right; vertical-align: bottom;}
.tdc_br {text-align: center; border-right: 1px solid black;}
.tdc_bb {text-align: center; border-bottom: 1px solid black;}
.tdhi3 {text-align: justify; border-left: 6em; padding-left: 8em;
text-indent:-2em;}
.tdr_brtd {text-align: right; border-right: 1px solid black;
border-top: 1px dotted black;}
.tdr_br {text-align: right; border-right: 1px solid black;}
.tdc_blr {text-align: center; border-left: 1px solid black; border-right: 1px solid black;}
.tdr_blr {text-align: right; border-left: 1px solid black; border-right: 1px solid black;}
.tdc_blrb {text-align: center; border-left: 1px solid black; border-right: 1px solid black;
border-bottom: 1px solid black;}
.tdr_blrb {text-align: right; border-left: 1px solid black; border-right: 1px solid black;
border-bottom: 1px solid black;}
.tdr_bb {text-align: right; border-bottom: 1px solid black;}
.tdc_bb {text-align: center; border-bottom: 1px solid black;}
.tdl_br {text-align: left; border-right: 1px solid black;}
.tdl_brtd {text-align: left; border-right: 1px solid black;
border-top: 1px dotted black;}
.tdr_brb {text-align: right; border-right: 1px solid black; border-bottom: 1px solid black;}
.tdl_brb {text-align: left; border-right: 1px solid black; border-bottom: 1px solid black;}
.tdc_brb {text-align: center; border-right: 1px solid black; border-bottom: 1px solid black;}
.pagenum {/* uncomment the next line for invisible page numbers */
/* visibility: hidden;*/
position: absolute;
left: 92%;
font-size: smaller;
text-align: right;
}/* page numbers */
.blockquot {
margin-left: 5%;
margin-right: 10%;
}
.center {text-align: center;}
.right {text-align: right;}
.smcap {font-variant: small-caps;}
.fs2 {font-size: 70%;}
.fs3 {font-size: 90%;}
/* Images */
img {border: none; max-width: 100%}
.caption {font-size: smaller; font-weight: bold;}
.figcenter {
margin: auto;
text-align: center;
page-break-inside: avoid;
max-width: 100%;
}
.figleft {
float: left;
clear: left;
margin-left: 0;
margin-bottom: 1em;
margin-top: 1em;
margin-right: 1em;
padding: 0;
text-align: center;
page-break-inside: avoid;
max-width: 100%;
}
/* comment out next line and uncomment the following one for floating figleft on ebookmaker output */
/*.x-ebookmaker .figleft {float: none; text-align: center; margin-right: 0;}*/
.x-ebookmaker .figleft {float: left;}
/* Footnotes */
.footnotes {border: dashed 1px;}
.footnote {
margin-left: 10%;
margin-right: 10%;
font-size: 0.9em;
}
.footnote .label {
position: absolute;
right: 84%;
text-align: right;
}
.fnanchor {
vertical-align: super;
font-size:.8em;
text-decoration: none;
white-space: nowrap
}
/* Transcriber's notes */
.transnote {
background-color:#E6E6FA;
color: black;
font-size:smaller;
padding:0.5em;
margin-bottom:5em;
font-family:sans-serif, serif;
}
.illowp50 {width: 50%;}
.illowp100 {width: 100%;}
.illowp20 {width: 20%;}
.illowp25 {width: 25%;}
.illowp80 {width: 80%;}
</style>
</head>
<body>
<div>*** START OF THE PROJECT GUTENBERG EBOOK 69062 ***</div>
<div class="transnote">
<h3>Transcriber’s Notes</h3>
<p>Obvious typographical errors have been silently corrected.</p>
<p>The cover was prepared by the transcriber and is placed in the
public domain.</p>
</div>
<hr class="chap"/>
<p class="right fs2">Issued March 17, 1911.</p>
<p class="center">U. S. DEPARTMENT OF AGRICULTURE,<br />
<small>BUREAU OF ANIMAL INDUSTRY.—<span class="smcap">Bulletin 132.</span><br />
A. D. MELVIN,<span class="smcap">Chief of Bureau</span>.</small></p>
<h1>A BACTERIOLOGICAL STUDY
OF HAM SOURING.</h1>
<p class="center fs3">BY</p>
<p class="center">C. N. McBRYDE, M. D.,<br />
<span class="fs2"><i>Senior Bacteriologist, Biochemic Division</i>.</span></p>
<div class="figcenter illowp25" id="seal" style="max-width: 15.625em;">
<img src="images/seal.jpg" alt="Department seal"/>
</div>
<p class="center"><small>WASHINGTON:<br />
GOVERNMENT PRINTING OFFICE.<br />
1911.</small></p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="THE_BUREAU_OF_ANIMAL_INDUSTRY">THE BUREAU OF ANIMAL INDUSTRY.</h2>
</div>
<hr class="small"/>
<ul class="fs3">
<li><i>Chief</i>: <span class="smcap">A. D. Melvin</span>.</li>
<li><i>Assistant Chief</i>: <span class="smcap">A. M. Farrington</span>.</li>
<li><i>Chief Clerk</i>: <span class="smcap">Charles C. Carroll</span>.</li>
<li><i>Animal Husbandry Division</i>: <span class="smcap">George M. Rommel</span>, chief.</li>
<li><i>Biochemic Division</i>: <span class="smcap">M. Dorset</span>, chief.</li>
<li><i>Dairy Division</i>: <span class="smcap">B. H. Rawl</span>, chief.</li>
<li><i>Inspection Division</i>: <span class="smcap">Rice P. Steddom</span>, chief;<span class="smcap">R. A. Ramsay</span>,<span class="smcap">Morris Wooden</span>, and
<span class="smcap">Albert E. Behnke</span>, associate chiefs.</li>
<li><i>Pathological Division</i>: <span class="smcap">John R. Mohler</span>, chief.</li>
<li><i>Quarantine Division</i>: <span class="smcap">Richard W. Hickman</span>, chief.</li>
<li><i>Zoological Division</i>: <span class="smcap">B. H. Ransom</span>, chief.</li>
<li><i>Experiment Station</i>: <span class="smcap">E. C. Schroeder</span>, superintendent.</li>
<li><i>Editor</i>:<span class="smcap">James M. Pickens</span>.</li>
</ul>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="LETTER_OF_TRANSMITTAL">LETTER OF TRANSMITTAL.</h2>
</div>
<p class="center pnb">
<span class="smcap">United States Department of Agriculture,</span></p>
<p class="psig pnb">Bureau of Animal Industry,</p>
<p class="right"><i>Washington, D. C., November 2, 1910</i>.
</p>
<p><span class="smcap">Sir</span>: I have the honor to transmit and to recommend for publication
as a bulletin of this Bureau a paper entitled “A Bacteriological
Study of Ham Souring,” by Dr. C. N. McBryde, senior bacteriologist
in the Biochemic Division of this Bureau.</p>
<p>The souring of hams is a source of considerable loss in the meat-packing
industry, and the cause of this trouble has heretofore been
in doubt. Dr. McBryde’s paper presents the results of an exhaustive
study of the subject, from which it appears that he has succeeded in
discovering the true cause of the trouble. Besides a description of the
experimental work the paper discusses methods of preventing the
souring of hams and the proper disposal of those which have become
affected.</p>
<p class="pnb">
Respectfully,</p>
<p class="psig"><span class="smcap">A. D. Melvin</span>,<br />
<i>Chief of Bureau</i>.</p>
<p>Hon.<span class="smcap">James Wilson</span>,<br />
<span style="margin-left:4em"><i>Secretary of Agriculture</i>.</span></p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<p><span class="pagenum" id="Page_6">[Pg 6]</span></p>
<h2 class="nobreak" id="CONTENTS">CONTENTS.</h2>
</div>
<table class="standard" summary="">
<tr>
<td></td>
<td class="tdr">Page.</td>
</tr>
<tr>
<td class="tdl">Introductory</td>
<td class="tdr"><a href="#Page_7">7</a></td>
</tr>
<tr>
<td class="tdl">Method of curing hams</td>
<td class="tdr"><a href="#Page_8">8</a></td>
</tr>
<tr>
<td class="tdl">Definition of souring</td>
<td class="tdr"><a href="#Page_10">10</a></td>
</tr>
<tr>
<td class="tdl">Classification of sour hams and location of sour areas</td>
<td class="tdr"><a href="#Page_10">10</a></td>
</tr>
<tr>
<td class="tdl">Method of detecting sour hams</td>
<td class="tdr"><a href="#Page_12">12</a></td>
</tr>
<tr>
<td class="tdl">Theories in regard to ham souring</td>
<td class="tdr"><a href="#Page_12">12</a></td>
</tr>
<tr>
<td class="tdl">Previous experimental work to determine cause of ham souring</td>
<td class="tdr"><a href="#Page_13">13</a></td>
</tr>
<tr>
<td class="tdl">The present experiments</td>
<td class="tdr"><a href="#Page_14">14</a></td>
</tr>
<tr>
<td class="tdli1">Media employed</td>
<td class="tdr"><a href="#Page_14">14</a></td>
</tr>
<tr>
<td class="tdli1">Method of procedure in examining hams</td>
<td class="tdr"><a href="#Page_15">15</a></td>
</tr>
<tr>
<td class="tdli1">Results of examination of sour and sound hams</td>
<td class="tdr"><a href="#Page_16">16</a></td>
</tr>
<tr>
<td class="tdli1">Histological changes in sour hams</td>
<td class="tdr"><a href="#Page_17">17</a></td>
</tr>
<tr>
<td class="tdli1">Chemical analyses of sour and sound hams</td>
<td class="tdr"><a href="#Page_18">18</a></td>
</tr>
<tr>
<td class="tdli1">Bacteriological examination of sour and sound hams</td>
<td class="tdr"><a href="#Page_20">20</a></td>
</tr>
<tr>
<td class="tdli1">Inoculation experiments with hams</td>
<td class="tdr"><a href="#Page_21">21</a></td>
</tr>
<tr>
<td class="tdli1">Probable method by which ham-souring bacillus enters hams</td>
<td class="tdr"><a href="#Page_33">33</a></td>
</tr>
<tr>
<td class="tdli2">Possibility of infection prior to slaughter</td>
<td class="tdr"><a href="#Page_33">33</a></td>
</tr>
<tr>
<td class="tdli2">Possible infection from pickling fluids</td>
<td class="tdr"><a href="#Page_34">34</a></td>
</tr>
<tr>
<td class="tdhi3">Experiment to show whether infection takes place from the curing
pickle</td>
<td class="tdrb"><a href="#Page_34">34</a></td>
</tr>
<tr>
<td class="tdli2">Possible infection through manipulation or handling</td>
<td class="tdr"><a href="#Page_35">35</a></td>
</tr>
<tr>
<td class="tdhi3">Infection from ham thermometers</td>
<td class="tdr"><a href="#Page_35">35</a></td>
</tr>
<tr>
<td class="tdhi3">Experiment to show whether hams become infected from ham
thermometers</td>
<td class="tdrb"><a href="#Page_37">37</a></td>
</tr>
<tr>
<td class="tdli3">Infection from pumping needles</td>
<td class="tdr"><a href="#Page_41">41</a></td>
</tr>
<tr>
<td class="tdli3">Infection from billhooks</td>
<td class="tdr"><a href="#Page_42">42</a></td>
</tr>
<tr>
<td class="tdli1">Biological and morphological characteristics of the ham-souring bacillus</td>
<td class="tdr"><a href="#Page_43">43</a></td>
</tr>
<tr>
<td class="tdli2">Conditions favorable to growth</td>
<td class="tdr"><a href="#Page_43">43</a></td>
</tr>
<tr>
<td class="tdli2">Growth on different culture media</td>
<td class="tdr"><a href="#Page_43">43</a></td>
</tr>
<tr>
<td class="tdli2">Morphology</td>
<td class="tdr"><a href="#Page_46">46</a></td>
</tr>
<tr>
<td class="tdli2">Spore formation</td>
<td class="tdr"><a href="#Page_46">46</a></td>
</tr>
<tr>
<td class="tdli2">Resistance to heat and chemical agents</td>
<td class="tdr"><a href="#Page_47">47</a></td>
</tr>
<tr>
<td class="tdli2">Gas production</td>
<td class="tdr"><a href="#Page_47">47</a></td>
</tr>
<tr>
<td class="tdli2">Acid production</td>
<td class="tdr"><a href="#Page_48">48</a></td>
</tr>
<tr>
<td class="tdli2">Pathogenic properties</td>
<td class="tdr"><a href="#Page_48">48</a></td>
</tr>
<tr>
<td class="tdli2">Nature of the bacillus</td>
<td class="tdr"><a href="#Page_48">48</a></td>
</tr>
<tr>
<td class="tdl">Prevention of ham souring</td>
<td class="tdr"><a href="#Page_50">50</a></td>
</tr>
<tr>
<td class="tdl">General summary and conclusions</td>
<td class="tdr"><a href="#Page_53">53</a></td>
</tr>
<tr>
<td class="tdl">Acknowledgments</td>
<td class="tdr"><a href="#Page_55">55</a></td>
</tr>
</table>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="ILLUSTRATIONS">ILLUSTRATIONS.</h2>
</div>
<hr class="small"/>
<p class="center fs3">PLATES.</p>
<table class="standard" summary="">
<tr>
<td></td><td></td>
<td></td>
<td class="tdr">Page.</td>
</tr>
<tr>
<td class="tdct"><span class="smcap">Plate</span></td>
<td class="tdrt"><a href="#Plate_I">I</a>. </td>
<td class="tdh">Fig. 1.—Section of muscular tissue from sound ham, showing muscle
fibers cut longitudinally; nuclei sharply defined and cross striation
distinct. Fig. 2.—Section of muscular tissue from sour ham,
showing muscle fibers cut longitudinally; nuclei undergoing disintegration and cross striation indistinct</td>
<td class="tdrb">16</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#Plate_II">II</a>. </td>
<td class="tdh">Fig. 1.—Section through muscular tissue of ham which has undergone
natural or spontaneous souring, showing distribution of
bacilli between the muscle fibers, which are cut obliquely.
Fig.2.—Section through muscular tissue of ham which has undergone
natural or spontaneous souring, showing individual bacilli between
the muscle fibers, which are cut somewhat obliquely</td>
<td class="tdrb">18</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#Plate_III">III</a>. </td>
<td class="tdh">Fig. 1.— Section through muscular tissue of artificially soured ham, showing
distribution of bacilli between the muscle fibers, which are shown
in cross section. Fig. 2.—Section through muscular tissue of
artificially soured ham, showing individual bacilli between the
muscle fibers, which are cut longitudinally</td>
<td class="tdrb">26</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#Plate_IV">IV</a>. </td>
<td class="tdh">Glucose bouillon culture in Smith fermentation tube at four days</td>
<td class="tdrb">48</td>
</tr>
<tr>
<td class="tdc" colspan="4">TEXT FIGURES.</td>
</tr>
<tr>
<td class="tdct"><span class="smcap">Fig.</span></td>
<td class="tdrt"><a href="#fig1">1</a>. </td>
<td class="tdh">Cross section through body of ham, with sour areas indicated by shading
and dotted lines</td>
<td class="tdrb">11</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#fig2">2</a>. </td>
<td class="tdh">Cross section through body of ham to show method of sampling for
chemical analysis</td>
<td class="tdrb">18</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#fig3">3</a>. </td>
<td class="tdh">Cross section through body of artificially soured ham, showing sour
areas and points at which cultures were taken</td>
<td class="tdrb">25</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#fig4">4</a>. </td>
<td class="tdh">Diagrammatic views showing construction of ham thermometer</td>
<td class="tdrb">36</td>
</tr>
<tr>
<td class="tdrt" colspan="2"><a href="#fig5">5</a>. </td>
<td class="tdh">Ham-souring bacillus (<i>Bacillus putrefaciens</i>), grown on egg-pork medium</td>
<td class="tdrb">46</td>
</tr>
</table>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<p><span class="pagenum" id="Page_7">[Pg 7]</span></p>
<p class="half-title">A BACTERIOLOGICAL STUDY OF HAM SOURING.</p>
<hr class="small"/>
<h2 class="nobreak" id="INTRODUCTORY">INTRODUCTORY.</h2>
</div>
<p>The souring of hams is a matter of considerable importance to those
engaged in the meat-packing industry, and has been the occasion
of no little worry, as in even the best-regulated packing establishments
the yearly losses it entails are considerable. The subject
has given rise to much speculation on the part of those engaged in the
curing of meats, as to the cause of the trouble and how it may be
remedied, and has received considerable attention in a practical way,
but little seems to have been done in a scientific way toward determining
the cause and nature of ham souring.</p>
<p>In a well-regulated meat-packing establishment the loss from ham
souring is usually figured at about one-tenth of 1 per cent of the total
weight of hams cured. At first thought this would seem but a small
loss, but when one reflects that in a single large packing establishment
some 3,000,000 hams are cured during the year, the loss, when figured
out, is considerable. Taking 15 pounds as the average weight of a
ham, 3,000,000 hams would represent 45,000,000 pounds of meat.
Figuring the loss from souring on the basis mentioned, the amount of
meat condemned and destroyed during the year would be 45,000
pounds. Assuming that hams sell at an average wholesale price of
15 cents a pound, the yearly loss for a single plant which cures
3,000,000 hams a year would be nearly $7,000.</p>
<p>While one-tenth of 1 per cent of the total weight of hams cured
would represent the loss from souring in a well-regulated establishment,
statistics obtained through Government meat inspectors show
that 0.25 per cent would more nearly represent the loss for the entire
country. During the fiscal year from July 1, 1908, to June 30, 1909,
some 670,000,000 pounds of hams were placed in cure in packing
establishments subject to Government inspection. Estimating the
loss from souring at 0.25 per cent, the total amount of meat condemned
and destroyed as sour would be 1,675,000 pounds. At 15
cents a pound the total annual loss from ham souring in packing
houses subject to Government inspection would figure up something
over a quarter of a million of dollars.</p>
<p>The problem of ham souring, therefore, is quite an important one
from a practical and financial standpoint; but aside from these considerations
it is also a subject of considerable scientific interest, and<span class="pagenum" id="Page_8">[Pg 8]</span>
in view of the fact that all sour meats are condemned under the Federal
regulations governing meat inspection it has seemed fitting that
this question should be made the subject of scientific investigation on
the part of the Bureau which is charged with the administration of
this inspection.</p>
<p>The investigation reported in this paper has been conducted chiefly
along bacteriological lines, and has been confined entirely to the wet
method of curing hams, as this method is the one generally used in
American packing houses.</p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="METHOD_OF_CURING_HAMS">METHOD OF CURING HAMS.</h2>
</div>
<p>In order to make clear certain points in regard to the nature and
occurrence of ham souring and to insure a better understanding of the
experiments which are to be described later, it would seem best to
begin with a brief outline of the method of curing hams as practiced
in the larger packing establishments of the country. This description
is merely a general outline of the method of preparing hams for cure
and the method of handling hams while in cure, and deals chiefly with
those points that bear on the question of souring.</p>
<p>After the slaughtered animal has been cleaned, scraped, eviscerated,
washed, and split down the middle, the carcass is usually
allowed to hang for an hour or so in a large room open to the outside
air, known as the “hanging floor.” This is done with a view to
getting rid of a certain amount of the body heat before the carcass is
run into the chill rooms, and effects a saving in refrigeration.</p>
<p>The carcasses are next run into “coolers” or chill rooms, and subjected
to refrigeration with a view to ridding them entirely of their
body heat. The coolers are large rooms fitted with brine pipes and
capable of accommodating several hundred carcasses. The temperature
of the coolers when the carcasses are run in is about 32° F.
When filled, the temperature of the cooler rises to about 45° F., owing
to the heat given off from the carcasses. The temperature is then
gradually reduced to 28 or 30° F. Hog carcasses are left in the coolers
as a rule for forty-eight hours, at the end of which time they are stiff
and firm, but not frozen. The temperature of the chill rooms is
always carefully watched, thermometer readings being made every
few hours and duly recorded. The temperature of the carcasses is
always tested when they leave the chill room. In those plants provided
with a hanging floor, a certain number of the carcasses are also
tested before they are sent to the chill rooms in order to determine
the amount of heat lost on the hanging floor.</p>
<p>The carcasses are tested by means of an especially constructed
thermometer, known as a “ham thermometer,” which has a pointed
metal protector so that it can be thrust into the body of the ham.
(See fig. 4.) The ham has been rightly selected as the proper portion<span class="pagenum" id="Page_9">[Pg 9]</span>
of the carcass at which to take the temperature, as it constitutes the
largest mass of muscular tissue in the carcass and holds the body heat
longer than any other portion. In taking the temperature, the thermometer
is thrust deep into the body of the ham so that the point of
the thermometer rests alongside or a little behind the upper portion
of the femur or middle bone, the latter being used as a guide in introducing
the thermometer. A certain number of the carcasses from
each cooler are tested in this way as a check on the refrigeration. The
inside temperature of the hams when they leave the chill rooms
should be about 34° F.</p>
<p>The carcasses are next cut up and the hams trimmed for pickling.
In some houses the hams are given an additional chilling of 48 hours
after they are cut from the carcasses, but this is not done as a rule,
nor does it seem to be necessary.</p>
<p>The hams are now sent to the pickling rooms, or “sweet pickle
department,” as this branch of the packing house is designated, and
here a certain number are again tested with a thermometer, as described
above. This test is carried out by the foreman in charge of the
sweet pickle department in order that he may satisfy himself that the
hams are properly chilled before they go into the pickle and as an
additional check on the refrigeration.</p>
<p>The hams are now ready to be “pumped,” and this pumping, as
will be shown later, constitutes an important step in a successful cure.
Pumping consists in forcing a strong brine solution containing saltpeter
into the muscular tissues of the ham, and is accomplished by
means of a large, hollow, fenestrated needle connected by means of a
rubber hose with a powerful hand pump. The needle is introduced
along the bone, the latter being used as a guide.</p>
<p>In all of the larger packing establishments two general methods of
curing hams are followed, the two methods being designated as the
“fancy” or “mild cure” and the “regular cure,” the term “cure”
being used to designate the curing period. Various trade names are
given by the different packing establishments to the hams cured by
these methods. In the fancy cure the hams are pumped in the shank
only, whereas in the regular cure they are pumped in both body and
shank. The same pumping pickle is generally used for the two cures.
It is a significant fact that the greater proportion of the “sours” are
found among the fancy or mild cure hams. This point will be discussed
farther on in connection with some experiments to be described later.</p>
<p>The actual curing is usually carried out in large vats which hold
about 1,400 pounds of meat or some hundred hams. The hams are
packed in the vats in layers and are entirely covered with the pickling
solution or brine. A certain proportion is always observed between
the weight of the meat and the amount of the solution. The pickling
solution, or “pickle,” as it is termed, is a brine solution containing<span class="pagenum" id="Page_10">[Pg 10]</span>
saltpeter and sugar. The composition of the pickle varies somewhat
with the different packing establishments. The fancy-cure hams are
usually cured in a milder pickle, that is, one that contains less salt
and saltpeter than the pickle used in the regular cure, although in
some packing establishments the same curing pickle is used for the
two cures, the only difference being the additional pumping given the
regular-cure hams. The pickling rooms, or “cellars,” as they are
called, are held at a temperature of 34° to 36° F., and the pickling
solutions are always chilled to this temperature before being used.</p>
<p>The hams are allowed to remain in cure for about 60 days, and
during this time are “overhauled” several times. Overhauling consists
in throwing the hams from the vat in which they are packed into
a neighboring empty vat, and then transferring the pickle to the new
vat. The pickle is not changed, and the same pickle follows the hams
through the entire curing process. The object in overhauling is to
stir up the pickle and expose fresh surfaces of the meat to its action.</p>
<p>Hams are also cured in tierces which hold about 300 pounds of
meat. In the tierce cure, the hams are packed in the tierces, the
latter are then headed up, the pickling solution is next run in through
the bunghole, so as to fill the tierce entirely, and a wooden stopper
is finally driven into the bunghole. The tierces are rolled back and
forth across the floor on dates corresponding to the dates of overhauling
in the vat cure. The object of the rolling is to stir up the
pickle, and in this way it corresponds to overhauling in the vat cure.</p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="DEFINITION_OF_SOURING">DEFINITION OF SOURING.</h2>
</div>
<p>To the meat inspector, a sour ham is one which has a tainted or
“off” odor, that is, any odor which deviates from the normal. The
odor may be very slight, so slight that at times only the trained meat
inspector can detect it. When slight, the odor is elusive and hard to
define, but when pronounced it has a distinctly putrefactive quality.
When not very pronounced, the odor possesses, as a rule, a slightly
sour quality, chemically speaking, and at times this sour quality may
be quite marked; hence the term “sour ham,” or “sour” has originated.
In a badly soured ham—using the term “sour” in the
packing-house sense to denote any ham that is tainted—the odor
loses this sour quality and becomes distinctly putrefactive in nature.</p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="CLASSIFICATION_OF_SOUR_HAMS_AND_LOCATION_OF_SOUR_AREAS">CLASSIFICATION OF SOUR HAMS AND LOCATION OF SOUR AREAS.</h2>
</div>
<p>Sour hams are classed as “shank sours” and “body sours,” according
to the location of the souring, and these may be “light” or
“heavy.” When the souring is very pronounced, the ham is termed
a “stinker.”</p>
<p>Souring appears to start, as a rule, around the stifle joint (femorotibial
articulation), and extends upward into the body of the ham.</p>
<p><span class="pagenum" id="Page_11">[Pg 11]</span></p>
<p>In quite a large proportion of the hams which are sour in the body—probably
from 40 to 50 per cent—the souring extends through to the
bone marrow of the femur or middle bone, and the sour odor is at
times more pronounced in the bone marrow than in the meat. The
odor of the bone marrow, when pronounced, is strongly suggestive of
a dissecting-room odor, and is distinctly putrefactive in quality.</p>
<p>In the case of light body sours the sour odor is confined to a small
area immediately around the bone, and may be so slight that it is
detected only with difficulty. In such hams the bone marrow is apt
to be sweet, and it is not until the souring becomes more extensive
that the bone marrow becomes involved.</p>
<div class="figcenter illowp100" id="fig1" style="max-width: 62.5em;">
<img class="w100" src="images/fig1.jpg" alt=""/>
<div class="caption"><span class="smcap">Fig. 1.</span>—Cross section through body of ham, with sour areas indicated by shading and dotted lines.</div>
</div>
<p>The distribution of the sour area in the body of a well-developed
sour is shown in figure 1.</p>
<p>In the case of a well-developed body sour the sour area is more
pronounced near the bone, as represented in figure 1 by the shaded
area, and may extend out into the body of the ham for a variable
distance, according to the degree of souring, as represented by the
dotted lines, gradually fading off toward the margins, where it may
be imperceptible or entirely wanting.</p>
<p>In the pronounced sours, termed “stinkers,” the odor pervades the
entire ham, and is of a distinctly putrefactive quality.</p>
<p>In shank sours, the souring is more or less confined to the shank,
or the region about the tibio-femoral articulation, but may extend
upward into the lower portion of the body of the ham.</p>
<p><span class="pagenum" id="Page_12">[Pg 12]</span></p>
<h3>METHOD OF DETECTING SOUR HAMS.</h3>
<p>Souring is detected and located by means of a pointed metal instrument
known as a “ham trier,” which resembles a long, slightly flattened
ice pick. The trier is thrust into the ham at different points
along the bone, rapidly withdrawn, and the odor which clings to the
metal noted. The trained inspector works very rapidly, and is
able to detect even the slightest sour or off odor which might be
imperceptible to one not trained to the work. At the end of the
cure all hams are tested with the trier under the supervision of
Government meat inspectors.</p>
<p>Hams are also given what is called the “30-day inspection” by
plant inspectors during the process of curing. An average ham
weighing from 14 to 16 pounds requires about 60 days to cure, and at
the end of 30 days a certain number of hams in each run are usually
tested to see how the cure is progressing. If no sour hams are
discovered at this inspection the packer knows that the cure is progressing
satisfactorily, and moreover he feels sure that his hams will
finish satisfactorily, for experience has taught him that souring develops
within the first four weeks of the curing period, and if his hams are
sweet at the end of this time, he can feel practically sure that no sours
will develop later on.</p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="THEORIES_IN_REGARD_TO_HAM_SOURING">THEORIES IN REGARD TO HAM SOURING.</h2>
</div>
<p>The theories as to the cause of souring are many and varied. The
majority of them are pure speculation and have no foundation upon
observed facts. A few of these theories may be enumerated to show
how wide and varied has been the speculation upon this subject.</p>
<p>A theory which is quite prevalent among packing-house employees
attributes souring to overheating of the animal previous to slaughter,
but tests were made by driving hogs to the point of exhaustion just
prior to slaughter and curing the hams from these animals in comparison
with hams taken from animals which had been rested prior
to slaughter, with no difference in the cured product; that is, the
hams taken from overheated hogs cured equally as well as those
taken from rested hogs.</p>
<p>Another theory attributes souring to a diseased condition of the
meat. Prior to the enforcement of the Federal regulations governing
meat inspection there might have been some ground for such a supposition,
but this theory could not hold at the present time, in view
of the thorough and efficient inspection now in force, for it can be
safely said that no diseased meat now passes the Government inspectors,
and therefore no diseased meat goes into cure in inspected houses.
In order to test this theory, however, hams were secured from a
number of condemned animals which showed various diseased conditions,
such as hog cholera, pyemia, septicemia, scirrhous chord, etc.,
and these hams were cured in comparison with hams taken from<span class="pagenum" id="Page_13">[Pg 13]</span>
normal hogs. It was found that the hams taken from the diseased
hogs cured equally as well as those taken from healthy hogs. The
hams from the diseased hogs were destroyed after the experiment, as
the meat taken from diseased animals was of course not considered
fit for consumption, the object of the experiment being merely to
determine whether or not souring is caused by diseased conditions.</p>
<p>Another theory attributes souring to imperfect or too rapid chilling
of the meat before it is put in pickle, and places the blame upon the
refrigeration. According to this theory, souring results when the
meat is chilled too suddenly, the idea being that by the rapid congealing
of the juices of the meat a coating is formed on the outside
of the ham whereby the animal heat is prevented from escaping from
the interior, leaving the meat next to the bone at a higher temperature
than the outside of the ham.</p>
<p>In order to test this last theory, a number of hog carcasses were
run direct from the killing floor to a cooler at 28° F. and a like
number of carcasses of the same average weight which had been
allowed to stand for two hours at the outside temperature of
the air (53° F.) were placed in the same cooler. The carcasses
which had hung for two hours in the air had lost an average of
14 degrees in temperature before going to the cooler. The temperature
of the cooler rose to 29° F. after the carcasses were put
in, but was soon reduced to 28° F. and held at this temperature.
The temperatures of the hams were taken at the end of 24 hours, and
practically no difference was found in the inside temperatures of the
two lots; that is, the hams on the hot carcasses which were subjected
to a sudden chilling exhibited practically the same inside temperature
(i. e., next to the bone) as those which had cooled for two hours at
the temperature of the air before being placed in the cooler.</p>
<p>Still another theory attributes souring to lack of penetration of the
pickling fluids, but analyses of sour and sound hams do not seem to
bear out this theory. The rate of penetration of the pickling fluids,
however, would seem to have some bearing on the subject, and this
point will be discussed later in connection with some laboratory
experiments on the inhibitory effects of sodium chlorid and potassium
nitrate.</p>
<p>So much for the more commonly accepted theories which have
been advanced to explain ham souring.</p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="PREVIOUS_EXPERIMENTAL_WORK_TO_DETERMINE_CAUSE_OF">PREVIOUS EXPERIMENTAL WORK TO DETERMINE CAUSE OF
HAM SOURING.</h2>
</div>
<p>A review of the literature reveals but one article bearing directly
on the subject of the cause of ham souring.</p>
<p>In June, 1908, Klein<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">[1]</a> published in the London Lancet an article
on “miscured” hams. He describes a miscured ham as one which
<span class="pagenum" id="Page_14">[Pg 14]</span>has a distinctly putrid smell, and the tainted areas he describes as
varying in color from a dirty gray to a dirty green, the muscular
tissues in the strongly tainted areas being swollen and soft, or jelly-like.
From such hams he isolated a large nonmotile, nonspore-bearing,
anaerobic bacillus which he calls <i>Bacillus fœdans</i>. He cultivated the
organism on different media and obtained from the cultures a putrid
odor resembling that of the ham from which the culture was obtained,
but did not attempt to produce tainting by injecting sound hams
with the bacillus.</p>
<div class="footnote">
<p><a id="Footnote_1" href="#FNanchor_1" class="label">[1]</a> Klein, E. On the nature and causes of taint in miscured hams. The Lancet, vol. 174, London, June
27, 1908.</p>
</div>
<p>While there can be little doubt that Klein’s bacillus was the cause
of the tainting in those hams which he examined, the proof would
certainly have been stronger had he injected sound hams with cultures
and thus proven that he could reproduce tainting experimentally
by means of his bacillus. Klein examined only dry-cured hams and
does not state the temperature at which they were cured. He fails
to offer any explanation as to how the bacillus gained entrance into
the hams.</p>
<hr class="chap x-ebookmaker-drop"/>
<div class="chapter">
<h2 class="nobreak" id="THE_PRESENT_EXPERIMENTS">THE PRESENT EXPERIMENTS.</h2>
</div>
<h3>MEDIA EMPLOYED.</h3>
<p>After considerable experimentation as to a suitable culture medium
for the bacteriological study of sour hams, a modification of the “egg-meat
mixture” used by Rettger<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">[2]</a> in his studies on putrefaction was
found to be the most satisfactory. This medium, which consists of
chopped meat and egg albumen, furnishes an excellent medium for
the growth of putrefactive organisms which rapidly break down the
proteids of the meat, giving rise to the characteristic odors of putrid
decomposition. Rettger used chopped beef and egg albumen, but for
the present work chopped pork was substituted for the beef, as affording
a more suitable medium for the growth of organisms accustomed
to growth in pork hams. The modified medium is prepared as follows:</p>
<div class="footnote">
<p><a id="Footnote_2" href="#FNanchor_2" class="label">[2]</a> Rettger, L. F. Studies on putrefaction. Journal of Biological Chemistry, vol. 2, 1906.</p>
</div>
<p>A. One-half pound of lean pork, freed from excess of fat and
sinew, is finely chopped in a meat chopper, 250 cubic centimeters of
water is then added, the meat acids are neutralized with sodium carbonate,
and the mixture is heated in an Arnold sterilizer for 30
minutes, with occasional stirring. It is then set away in a cold
place for several hours. A small amount of fat collects at the top in
the form of a fatty scum, as it is impossible to remove all of the fat
from the meat before it is chopped. The fatty scum, which hardens
upon standing in the cold, is now removed.</p>
<p>B. The whites of three eggs are mixed with 250 cubic centimeters
of water. The mixture is rendered neutral to phenolphthalein by
means of dilute hydrochloric acid and heated for 30 minutes in the
Arnold sterilizer, with occasional stirring.</p>
<p><span class="pagenum" id="Page_15">[Pg 15]</span></p>
<p>A and B are now mixed and 2.5 grams (0.5 per cent) of powdered
calcium carbonate added. The mixture is next run into large sterile
test tubes, or sterile flasks, and sterilized in an Arnold sterilizer on
three successive days.</p>
<p>In addition to the egg-pork mixture described above, culture tubes
of agar and bouillon prepared from pork instead of beef, with the
addition of 1 per cent of glucose, were also used; but the best results
were obtained with the egg-pork medium, as with this medium, the
early development of sour or putrefactive odors furnished a valuable
indication as to the presence of organisms capable of producing sour
or putrefactive changes in meat.</p>
<h3>METHOD OF PROCEDURE IN EXAMINING HAMS.</h3>
<p>The hams were sectioned through the body, the femur, or “middle
bone,” as it is known in packing-house parlance, being cut at a point
about 1-1/2 or 2 inches below its head. A cross section of a ham thus
cut is shown in figure 1. After sectioning, the hams were subjected
to a microscopical, bacteriological, and chemical examination as
follows:</p>
<p><i>Microscopical examination.</i>—Bits of muscular tissue, taken from
various points, were teased out in salt solution and the condition of
the muscle fibers noted. Smear preparations were also made from
bits of muscular tissue and from the bone marrow, and these were
stained and subjected to microscopical examination. Portions of
the meat were also hardened and cut into microscopic sections, which
were stained and mounted for histological and bacteriological study.</p>
<p><i>Bacteriological examination.</i>—In the bacteriological examination
of sour hams, especial attention was directed to the detection of
anaerobic species, as it seemed reasonable to suppose that if the
changes taking place in sour hams were due to bacteria these bacteria
would in all likelihood be anaerobes (i. e., organisms which develop
in the absence of oxygen). This assumption was based upon the fact
that, as a rule, souring begins in the interior of the ham next to the
bone, and, furthermore, the hams are cured in large vats where they
are completely submerged in the pickling fluids, so that any bacteria
which develop within the bodies of the hams while they are in cure
are probably restricted to practically anaerobic conditions.</p>
<p>Cultures were made from the interiors of the hams at various points
by first searing the cut surface thoroughly with a heavy metal spatula
and then cutting out, by means of sterile scissors and forceps, plugs
of meat about 1 cm. square. The plugs of meat were then dropped
into tubes containing the egg-pork medium and pushed down to the
bottom of the tubes, where they were held in place by the chopped
meat above; in this way conditions favorable for the development
of anaerobic organisms were obtained. In inoculating the pork-agar<span class="pagenum" id="Page_16">[Pg 16]</span>
tubes, the medium was first boiled to expel any inclosed air and cooled
to 43° to 45° C; the plugs of meat were then dropped into the tubes
and the agar rapidly solidified by plunging the tubes in cold water;
in this way the bits of meat were inclosed in the agar at the bottom
of the tubes, affording suitable conditions for anaerobic growth.
Aerobic and anaerobic plates were also made from the meat, and in
most cases bouillon tubes were also inoculated. Cultures were always
taken from the bone marrow as well as from the meat. Novy jars
were also used for obtaining anaerobic conditions in growing the cultures.</p>
<p><i>Chemical examination.</i>—In order to determine whether the souring
was connected with or dependent upon a lack of penetration of the
pickling fluids to the interior of the meat, the hams were further subjected
to a chemical examination and the content of the meat in
sodium chlorid and potassium nitrate determined at varying depths.</p>
<h3>RESULTS OF EXAMINATION OF SOUR AND SOUND HAMS.</h3>
<p>The sour hams examined were obtained from four different packing
establishments. All of the hams studied were “sweet-pickle hams”
which had not been smoked. The sour hams selected for examination
were good typical body sours, in which the sour odor was well developed,
but not of the very pronounced or putrefactive type.</p>
<p>The sour odor in every case was found to be more pronounced next
to the bone, being usually rather more pronounced just behind the
bone, that is, on the fat side of the bone. The sour odor in each
instance was confined to an area of meat immediately surrounding
the femur and extending out through the body of the ham for a variable
distance, as shown by the dotted lines in figure 1, but in no case
did the sour odor extend all the way to the margin of the meat, nor
did it as a rule extend below the tibio-femoral articulation, the shank
proper and the bone marrow of the shank (i. e., of the tibia) being
usually sweet. The butt portion of the hams—that portion above
and behind the hitch bone (symphasis pubis)—was also sweet.</p>
<p>Immediately after sectioning, the sour areas, as a rule, could be
readily distinguished by a difference in color. In the freshly cut hams
the muscular tissue near the bone, where the sour odor was more
pronounced, exhibited a slight but distinct grayish hue, at times having
a slight greenish tinge; in other words, the muscular tissue in the
sour areas lacked the normal bright red color of the sound meat and
was distinctly lighter in color than the surrounding tissues. Upon
exposure to air, however, the lighter, grayish, sour areas tend to
assume a reddish hue and become much less pronounced than in the
freshly cut ham. After the cut surface of the ham has been exposed
to the air for some time it may be difficult to distinguish the sour
areas by any difference in color.</p>
<p class="center small">
<span class="smcap">Bul. 132, Bureau of Animal Industry, U. S. Dept. of Agriculture. <a id="Plate_I"></a>Plate I.</span></p>
<div class="figcenter illowp80" id="pl1a" style="max-width: 50em;">
<a href="images/pl1alge.jpg">
<img src="images/pl1a.jpg" alt=""/></a>
<div class="caption"><p class="hang"><span class="smcap">Fig. 1.—Section of Muscular Tissue from Sound Ham, Showing
Muscle Fibers Cut Longitudinally; Nuclei Sharply Defined
and Cross Striation Distinct.</span></p>
<p class="center small">(Pen-and-ink drawing made with camera lucida from section stained with
hematoxylin and eosin to show histological structure.× 320.)</p></div>
</div>
<div class="figcenter illowp80" id="pl1b" style="max-width: 50em;">
<a href="images/pl1blge.jpg">
<img src="images/pl1b.jpg" alt=""/></a>
<div class="caption"><p class="hang"><span class="smcap">Fig. 2.—Section of Muscular Tissue from Sour Ham, Showing
Muscle Fibers Cut Longitudinally; Nuclei Undergoing Disintegration
and Cross Striation Indistinct.</span></p></div>
<p class="center small">(Pen-and-ink drawing made with camera lucida from section stained with
hematoxylin and eosin to show histological structure.× 320.)</p></div>
<p class="center small">
<span class="smcap small">Bul. 132, Bureau of Animal Industry, U. S. Dept. of Agriculture. <a id="Plate_II"></a>Plate II.</span></p>
<div class="figcenter illowp80" id="pl2a" style="max-width: 50em;">
<a href="images/pl2alge.jpg">
<img src="images/pl2a.jpg" alt=""/></a>
<div class="caption"><p class="hang"><span class="smcap">Fig. 1.—Section Through Muscular Tissue of Ham which has
Undergone Natural or Spontaneous Souring, Showing Distribution
of Bacilli Between the Muscle Fibers, which are Cut
Obliquely. The Dark Masses Between the Muscle Fibers
Represent Clumps of Bacilli.</span></p></div>
<p class="center small">(Pen-and-ink drawing made with camera lucida from section stained with
hematoxylin and eosin to show histological structure.× 320.)</p></div>
<div class="figcenter illowp80" id="pl2b" style="max-width: 50em;">
<a href="images/pl2blge.jpg">
<img src="images/pl2b.jpg" alt=""/></a>
<div class="caption"><p><span class="smcap">Fig. 2.—Section Through Muscular Tissue of Ham which has
Undergone Natural or Spontaneous Souring, Showing Individual
Bacilli Between the Muscle Fibers, which are Cut Somewhat
Obliquely. Nuclei have Lost Sharp Outline and Cross Striation
is Indistinct.</span></p></div>
<p class="center small">(Pen-and-ink drawing made with camera lucida from section stained with
hematoxylin and eosin to show histological structure.× 320.)</p></div>
<p><span class="pagenum" id="Page_17">[Pg 17]</span></p>
<p>In the sour areas near the bone the muscular tissue was distinctly
softer; that is, it broke and cut more readily than the surrounding
tissues. This was usually quite noticeable in cutting out plugs of
the meat for making cultures. In a ham which shows pronounced
souring the muscular tissues in the worst affected areas may become
quite soft and even slightly gelatinous.</p>
<p>The sour areas, when tested with litmus paper, frequently showed
a slight but distinct alkaline reaction. When aqueous extracts of
the sour meat, however, were titrated with phenolphthalein they
were found to be acid.</p>
<h3>HISTOLOGICAL CHANGES IN SOUR HAMS.</h3>
<p>In preparations made by teasing out bits of the meat in physiological
salt solution, the cross striation of the muscle fibers from the sour
areas was found to be much less distinct than in similar preparations
taken from sound portions of the meat or from sound hams. At
times it was found that the muscle fibers in the sour areas had completely
lost their cross striæ, but the longitudinal striation could still
be made out. In cases where the souring was pronounced there was
sometimes complete loss of both longitudinal and cross striation; in
these cases the muscle fibers appeared to have undergone slight swelling
and the protoplasm exhibited a finely granular appearance.</p>
<p>In stained sections of the sour meat another striking change was
noticed in the disintegration of the nuclei of the muscle fibers, which
are at times completely broken up, appearing as bluish granular
masses in sections stained with hematoxylin and eosin.(Compare
figs. 1 and 2 of Pl. I.)</p>
<p>In sections stained by the Gram-Weigert method to show the presence
of bacteria, a large Gram-staining bacillus was noted between
the muscle fibers in the connective-tissue elements of the muscle.
In some of the sections these bacilli were present in great numbers,
sometimes in densely packed clumps or masses, while in other sections,
or in other portions of the same section, they were only sparsely distributed
between the muscle fibers. Where the bacteria were more
numerous the histological changes in the muscle fibers, especially the
breaking down of the nuclei, were more noticeable. The intermuscular
connective tissue had apparently furnished paths of least resistance
along which the organism followed. In <a href="#Plate_II">Plate II</a>, figures 1 and
2, the bacteria are shown between the muscle fibers under low and
high power magnifications.</p>
<p>In <a href="#Plate_II">Plate II</a>, figure 1, under the low-power magnification, the bacteria
appear as dark clumps or bands between the muscle bundles.
Under the high power they are shown following along the sarcolemma
sheaths between the muscle fibers.</p>
<p><span class="pagenum" id="Page_18">[Pg 18]</span></p>
<h3>CHEMICAL ANALYSES OF SOUR AND SOUND HAMS.</h3>
<p>In order to determine whether there was any difference in regard
to the penetration of the pickling fluids in the sour hams as compared
with sound hams, a series of four sour hams were subjected to a
chemical examination in comparison with four sound hams. All
were sweet-pickle hams and were obtained from the same packing
establishment. They were all of the same cure and the same approximate
age (i. e., length of cure) and the same approximate weight.</p>
<p>In taking samples for chemical analysis, the following procedure
was adopted: A section about 2-1/2 inches wide was cut from the center
of the body. The two ends of this section were then trimmed off
along the lines L-M and N-O, as shown in figure 2. Beginning at the
skinned surface, four slices, A, B, C, and D, were then made, as indicated
by the dotted lines. Slice B contained the bone in each
instance. Slice D was practically all fat. Each slice was ground
separately in a meat chopper and the sample thoroughly mixed before
taking out portions for analysis.</p>
<div class="figcenter illowp80" id="fig2" style="max-width: 50em;">
<img src="images/fig2.jpg" alt=""/>
<div class="caption"><span class="smcap">Fig. 2.</span>—Cross section through body of ham to show method of sampling for chemical analysis. A, slice
below bone; B, bone slice; C, slice above bone; D, fat slice.</div>
</div>
<p>As all of the hams examined were mild-cure hams, that is, had
been pumped in the shank only, the pickling fluids in order to reach
the bodies of these hams had to penetrate chiefly from the skinned
surface of the ham, as little if any penetration takes place through
the thick skin of the ham.</p>
<p>The analyses<a id="FNanchor_3" href="#Footnote_3" class="fnanchor">[3]</a> shown in the following tables therefore indicate the
degree of penetration of the pickling fluids.</p>
<div class="footnote">
<p><a id="Footnote_3" href="#FNanchor_3" class="label">[3]</a> These analyses were made by Mr. R. R. Henley, of the Biochemic Division, Bureau of Animal
Industry.</p>
</div>
<p><span class="pagenum" id="Page_19">[Pg 19]</span></p>
<p class="center"><i>Analyses of sour hams.</i></p>
<table class="standard" summary="">
<tr>
<th class="brdr tdc">No.</th>
<th class="brdr tdc">Description.</th>
<th class="brdr tdc">Slice.</th>
<th class="brdr tdc">NaCl.</th>
<th class="brdr tdc">KNO₃.</th>
</tr>
<tr>
<td></td>
<td class="tdc_blr"></td>
<td></td>
<td class="tdc_blr"><i>Per cent.</i></td>
<td class="tdc"><i>Per cent.</i></td>
</tr>
<tr>
<td class="tdr">1</td>
<td class="tdc_blr">Sour body</td>
<td class="tdc">A</td>
<td class="tdr_blr">6.18</td>
<td class="tdr">0.175</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">4.83</td>
<td class="tdr">.224</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">3.65</td>
<td class="tdr">.299</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">D</td>
<td class="tdr_blr">1.03</td>
<td class="tdr">.074</td>
</tr>
<tr>
<td class="tdr">2</td>
<td class="tdc_blr">do</td>
<td class="tdc">A</td>
<td class="tdr_blr">5.34</td>
<td class="tdr">.174</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">3.70</td>
<td class="tdr">.150</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">2.79</td>
<td class="tdr">.174</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">D</td>
<td class="tdr_blr">1.12</td>
<td class="tdr">.012</td>
</tr>
<tr>
<td class="tdr">3</td>
<td class="tdc_blr">do</td>
<td class="tdc">A</td>
<td class="tdr_blr">5.04</td>
<td class="tdr">.125</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">4.08</td>
<td class="tdr">.149</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">2.72</td>
<td class="tdr">.099</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">D</td>
<td class="tdr_blr">1.19</td>
<td class="tdr">.048</td>
</tr>
<tr>
<td class="tdr">4</td>
<td class="tdc_blr">do</td>
<td class="tdc">A</td>
<td class="tdr_blr">7.78</td>
<td class="tdr">.250</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">5.31</td>
<td class="tdr">.100</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">4.76</td>
<td class="tdr">.200</td>
</tr>
<tr>
<td class="tdr_bb"></td>
<td class="tdc_blrb"></td>
<td class="tdc_bb">D</td>
<td class="tdr_blrb">1.96</td>
<td class="tdr_bb">.048</td>
</tr>
</table>
<p class="center"><i>Analyses of sound hams.</i></p>
<table class="standard" summary="">
<tr>
<th class="brdr tdc">No.</th>
<th class="brdr tdc">Description.</th>
<th class="brdr tdc">Slice.</th>
<th class="brdr tdc">NaCl.</th>
<th class="brdr tdc">KNO₃.</th>
</tr>
<tr>
<td></td>
<td class="tdc_blr"></td>
<td></td>
<td class="tdc_blr"><i>Per cent.</i></td>
<td class="tdc"><i>Per cent.</i></td>
</tr>
<tr>
<td class="tdr">1</td>
<td class="tdc_blr">Sound</td>
<td class="tdc">A</td>
<td class="tdr_blr">5.80</td>
<td class="tdr">0.211</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">4.83</td>
<td class="tdr">.188</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">3.86</td>
<td class="tdr">.221</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">D</td>
<td class="tdr_blr">1.33</td>
<td class="tdr">.063</td>
</tr>
<tr>
<td class="tdr">2</td>
<td class="tdc_blr">do</td>
<td class="tdc">A</td>
<td class="tdr_blr">4.94</td>
<td class="tdr">.197</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">4.08</td>
<td class="tdr">.149</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">3.05</td>
<td class="tdr">.223</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">D</td>
<td class="tdr_blr">1.56</td>
<td class="tdr">.059</td>
</tr>
<tr>
<td class="tdr">3</td>
<td class="tdc_blr">do</td>
<td class="tdc">A</td>
<td class="tdr_blr">5.92</td>
<td class="tdr">.173</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">4.29</td>
<td class="tdr">.099</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">4.12</td>
<td class="tdr">.139</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">D</td>
<td class="tdr_blr">2.32</td>
<td class="tdr">.049</td>
</tr>
<tr>
<td class="tdr">4</td>
<td class="tdc_blr">do</td>
<td class="tdc">A</td>
<td class="tdr_blr">5.53</td>
<td class="tdr">.119</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">B</td>
<td class="tdr_blr">4.89</td>
<td class="tdr">.079</td>
</tr>
<tr>
<td class="tdr"></td>
<td class="tdc_blr"></td>
<td class="tdc">C</td>
<td class="tdr_blr">4.32</td>
<td class="tdr">.099</td>
</tr>
<tr>
<td class="tdr_bb"></td>
<td class="tdc_blrb"></td>
<td class="tdc_bb">D</td>
<td class="tdr_blrb">2.19</td>
<td class="tdr_brb">.041</td>
</tr>
</table>
<p>Taking an average of the four slices in each ham so as to get an
average for the entire ham, and comparing the sour hams with the
sound hams, we have the following comparison:</p>
<table class="standard" summary="">
<tr>
<td class="tdc"></td>
<td class="tdc"></td>
<td class="tdc">NaCl.</td>
<td class="tdc">KNO₃.</td>
</tr>
<tr>
<td class="tdl">Average for 4 sour hams (entire ham)</td>
<td class="tdc">per cent.</td>
<td class="tdr">3.84</td>
<td class="tdr">0.143</td>
</tr>
<tr>
<td class="tdl">Average for 4 sound hams (entire ham)</td>
<td class="tdc">do</td>
<td class="tdr">3.93</td>
<td class="tdr">.131</td>
</tr>
</table>
<p>These figures show practically no difference between the sour and
the sound hams as regards the sodium chlorid and potassium nitrate
content of the entire ham.</p>
<p>If, now, we compare the bone slices—and these afford really a
better basis for comparison, as in sour-body hams the souring is
always more pronounced around the bone—we have the following
figures:</p>
<table class="standard" summary="">
<tr>
<td class="tdc"></td>
<td class="tdc"></td>
<td class="tdc">NaCl.</td>
<td class="tdc">KNO₃.</td>
</tr>
<tr>
<td class="tdl">Average for 4 sour hams (bone slice)</td>
<td class="tdc">per cent.</td>
<td class="tdr">4.48</td>
<td class="tdr">0.155</td>
</tr>
<tr>
<td class="tdl">Average for 4 sound hams (bone slice)</td>
<td class="tdc">do</td>
<td class="tdr">4.52</td>
<td class="tdr">0.129</td>
</tr>
</table>
<p>Here, again, we find no essential difference between the sour and
the sound hams, and we must conclude from these analyses that
souring does not depend upon or result from a lack of penetration
of the pickling fluids.</p>
<p><span class="pagenum" id="Page_20">[Pg 20]</span></p>
<p>It seems probable that in mild-cure hams, which are pumped in the
shank only, the souring begins in the upper portion of the shank and
extends upward along the bone into the body of the ham, and that
it takes place before the pickling fluid has penetrated to the interior
of the ham. When the pickling fluid reaches the interior of the ham
it tends to inhibit the souring, which, as will be shown later, is due
to the development of bacteria within the bodies of the hams. The
growth of the bacteria, however, within the bodies of the hams and
the histological changes in the muscle fibers do not seem to interfere
with the penetration of the pickling fluids.</p>
<h3>BACTERIOLOGICAL EXAMINATION OF SOUR AND SOUND HAMS.</h3>
<p>In all of the sour hams which were examined bacteriologically a
large anaerobic bacillus was found to be constantly present. From
several of the hams this bacillus was obtained in pure culture; that is,
it was the only organism present in cultures made from the sour
meat and from the bone marrow of the femur. Such cultures, when
held at room temperature, gave, at three days, a sour-meat odor
exactly resembling that obtained from sour hams.</p>
<p>In many of the sour hams other bacteria were found in association
with the anaerobic bacillus noted above. These other bacteria, however,
were not constant, being sometimes present and sometimes
absent. Among the other bacteria noted in the sour hams, the
following forms occurred most frequently:</p>
<p>1. A nonmotile, gram-positive bacillus, measuring from 1.5 to 4
microns in length by 0.5 micron in breadth, sometimes in chains and
filaments.</p>
<p>2. A small, nonmotile, gram-negative bacillus, about the size of
<i>Bacillus coli</i> and usually in pairs.</p>
<p>3. A large micrococcus.</p>
<p>Sometimes one and sometimes all of these bacteria were present
in a given ham. They were encountered most frequently in hams
which had been pumped in both body and shank, and were probably
ordinary pickle bacteria. They were not strict anaerobes, but
belonged to the class of facultative or optional anaerobes; that is,
organisms which will grow either with or without free oxygen.
These bacteria were isolated and grown on the egg-pork medium,
but failed to give any characteristic sour or putrefactive odors, and
were therefore discarded.</p>
<p>A series of sound hams, all of them of mild cure—that is, hams
which had been pumped in the shank only—were also examined
bacteriologically. In examining these hams cultures were taken
at varying depths, beginning at the skinned surface and going backward
toward the fat. Cultures were also taken from the bone
marrow of the femur. In the cultures taken near the skinned<span class="pagenum" id="Page_21">[Pg 21]</span>
surfaces the ordinary pickle bacteria were obtained, but these did
not, as a rule, extend beyond a depth of 3 centimeters below the
skinned surface. The cultures taken from the deeper portions of
the hams and from the bone marrow of the femur were entirely
negative—that is, failed to show any growth—and the anaerobic
bacillus noted in the sour hams was not encountered in any of the
cultures made from these hams.</p>
<p>The anaerobic bacillus isolated from the sour hams was found
to correspond in morphology with the organism noted in the microscopic
sections made from the muscular tissue. In view of this
fact and the fact that it was constantly present in the sour hams
examined, and was capable of producing in egg-pork cultures a
sour-meat odor of the same nature as that obtained from sour hams,
this organism was subjected to further study and experimentation.</p>
<h3>INOCULATION EXPERIMENTS WITH HAMS.</h3>
<p>The experiments which follow were conducted at two different
packing establishments in one of the larger packing centers of the
country. The officials at each of these establishments showed
great interest in the experiments and were most courteous and
obliging in supplying the necessary materials.</p>
<p>The first question to be decided was whether the bacillus isolated
from sour hams was actually capable of causing ham souring. The
bacillus in question had, when cultivated on the egg-pork medium,
given rise to a sour odor similar to that obtained from sour hams,
but this was not regarded as proof positive that the organism was the
actual cause of souring in hams. The proper way to decide this
point seemed to be to inoculate hams with the bacillus and then
subject these hams to the regular method of cure and see whether
they became sour, just as the pathogenic properties of a disease-producing
organism are determined by the inoculation of experiment
animals. The first two experiments which follow were designed
to decide this point.</p>
<p>It was regarded as important to conduct similar experiments
at two different establishments, in order to determine whether the
same results would be obtained under the somewhat different conditions
imposed by different methods of cure. The two experiments
which follow were carried out, therefore, at different establishments.</p>
<h6><i>Experiment I.</i></h6>
<p>In carrying out this experiment four tierces of hams were “put
down” or “packed”—that is, placed in cure. Two of the tierces
were given the fancy or mild cure and two the regular or stronger cure.
The hams in two of the tierces, one mild and one regular cure, were
injected with a culture suspension of the bacillus; the other two tierces
were not injected with culture and were put down to serve as checks on<span class="pagenum" id="Page_22">[Pg 22]</span>
the cure. Hams weighing from 12 to 14 pounds were used for the mild
cure, while for the regular cure hams weighing from 14 to 16 pounds
were used. This was in accordance with the general rule which prevails
in packing houses, the lighter hams being subjected to the mild
cure and the heavier hams to the regular cure. The only difference
between the mild and the regular cure in this experiment lay in the
pumping. The hams which were given the mild cure were pumped
in the shank only, while those given the regular cure were pumped
in the body as well as in the shank.</p>
<p>All of the hams had received the usual 48-hour chill. They were
all pumped with the same pumping pickle and cured in the same
curing pickle, and were in cure for the same length of time. The
pumping and curing pickles used were the regular pumping and
curing pickles of the establishment at which the experiment was
carried out, and the hams were cured in accordance with the fancy
and regular cures as practiced at this establishment.</p>
<p>The hams were packed in new tierces which had been thoroughly
scalded with boiling water. The tierces were held in a curing room
which was kept at an average temperature of from 34° to 36° F.,
the temperature occasionally going as high as 38° and 40° F., but
never above 40° F. The hams were left in cure for about 70
days, which is a little longer than the usual cure. The tierces were
rolled three times during the cure. At the end of the cure the hams
in all four tierces were carefully tested by an expert meat inspector,
who knew nothing of the treatment which the hams had received.</p>
<p>The hams in two of the tierces were inoculated with a culture
suspension prepared as follows: Ten tubes of egg-pork medium, each
tube containing approximately 10 cubic centimeters of the medium,
were inoculated with the bacillus and held at room temperature
(20° to 25° C.) for six days. The cultures were then filtered through
sterile gauze into a large sterile flask; this was done in order to
remove the particles of meat, which might otherwise have clogged
the syringes used in inoculating the hams. In transferring the contents
of the culture tubes to the filter the tubes were washed out
with sterile physiological salt solution (0.6 per cent sodium chlorid),
and the meat particles on the filter were afterwards washed with
the salt solution, a sufficient quantity of the latter being used to
bring the total volume of filtrate to 400 cubic centimeters. A
microscopic preparation from the filtrate showed the organisms in
large numbers, with an occasional rod showing a large terminal
spore. This suspension was used for the injection of 40 hams, each
ham being given 10 cubic centimeters, or the equivalent of 2.5 cubic
centimeters of the original culture. The hams were injected with the
culture suspension by means of a sterile syringe carrying a long 5-inch
needle. The needle was thrust well into the body of the ham at a
point near the upper end of the middle bone or femur, the latter<span class="pagenum" id="Page_23">[Pg 23]</span>
being used as a guide in inserting the needle and the injection being
made into the tissues just behind and a little to one side of the
upper end of the femur.</p>
<p>The details of the experiment were as follows:</p>
<div class="blockquot">
<p><i>Tierce No. 1 (fancy cure).</i>—This tierce contained 20 hams weighing from 12 to 14
pounds each. These hams were pumped in the shank only. Immediately after
pumping they were injected with 10 cubic centimeters each of the liquid culture
or suspension described above. After injection the hams were immediately packed
in the tierce, which was then headed up, filled with the regular curing pickle, and
placed in cure.</p>
<p>Result: When tested at the end of the cure all of the hams in this tierce save one
were found to be sour. In 10 of them the souring was very marked throughout the
body of the ham and extended into the shank as well. In six the souring was very
marked in the body of the ham, but did not extend into the shank. In three there
was slight but well-marked souring in the body of the ham with no souring in the
shank, and one remained sweet. The probable explanation of the variation in
the degree and the extent of the souring will be discussed later. The bone marrow
of the femur or middle bone was tested in all of the hams and found to be sour in
18. In one of the hams which showed only slight souring in the body the souring
did not extend through to the bone marrow, and in the ham which remained sweet
the bone marrow was also sweet. The fact that one ham in this tierce remained
sweet was in all likelihood due to an oversight in making the inoculations. In making
the inoculations the hams were spread out in a row on a table by a packing-house
assistant, who removed the hams as soon as they were inoculated and placed them in
tierces; and it is more than probable that the assistant removed one of the hams before
it was inoculated in the interval when the writer was busy filling the syringe for
the next inoculation.</p>
<p><i>Tierce No. 2 (fancy cure).</i>—This tierce contained 20 hams of the same average weight
as the preceding. They were pumped in the shank only, but were not injected with
culture, being put down to serve as checks on the hams in tierce No. 1. These hams,
therefore, were subjected to exactly the same cure and were held under exactly the
same conditions as those in tierce No. 1, the only difference being that the hams in
this tierce were not injected with culture.</p>
<p>Result: When tested at the end of the cure all of the hams in this tierce were found
to be perfectly sound and sweet, showing that the curing in this instance was properly
carried out and that the souring of the hams in tierce No. 1 was undoubtedly due to
the injections of culture which they received.</p>
<p><i>Tierce No. 3 (regular cure).</i>—This tierce contained 20 hams weighing from 14 to
16 pounds each. These hams were pumped in the shank and also in the body. Immediately
after pumping they were each injected in the same manner as those in tierce
No. 1 with 10 cubic centimeters of culture. The hams were then packed in tierce and
placed in cure.</p>
<p>Result: At the end of the cure 9 of the hams were found to be sour, while 11
remained sweet. Of the 9 hams which became sour, 1 showed very pronounced souring
in the body and in the shank as well, 3 showed very pronounced souring in the
body, 1 showed pronounced souring in the body, and 4 slight souring in the body.
The bone marrow of the femur was tested in all of the sour hams and was found to be
sour in 7. In 2 of the sour hams which showed slight souring in the body the souring
noted in the meat had not extended through to the bone marrow.</p>
<p><i>Tierce No. 4 (regular cure).</i>—This tierce contained 20 hams of the same average weight
as those in tierce No. 3, and, like the latter, were pumped in both shank and body, but
were not injected with culture. This tierce was put down to serve as a check on
tierce No. 3 and was held under exactly the same conditions, the only difference being
that these hams were not injected with culture.</p>
<p><span class="pagenum" id="Page_24">[Pg 24]</span></p>
<p>Result: At the end of the cure the hams were carefully tested and all were found to
be perfectly sound and sweet.</p>
</div>
<p class="center"><i>Results of Experiment I.</i></p>
<table class="standard" summary="">
<tr>
<th class="tdc brdr" rowspan ="2">No. of tierce.</th>
<th class="tdc brdr" rowspan ="2">Number<br />of hams.</th>
<th class="tdc brdr" rowspan ="2">Average<br />weight of hams<br /><i>Pounds.</i></th>
<th class="tdc brdr" rowspan ="2">Cure.</th>
<th class="tdc brdr" rowspan ="2">How pumped.</th>
<th class="tdc brdr" rowspan ="2">Treatment.</th>
<th class="tdc brdr" colspan="2">Condition at end of cure.</th>
</tr>
<tr>
<th class="tdc brdr">Number of sour hams</th>
<th class="tdc brdr">Percentage of sour hams</th>
</tr>
<tr>
<td class="tdr_br"> 1</td>
<td class="tdr_br">20</td>
<td class="tdr_br">12-14</td>
<td class="tdr_br">Fancy</td>
<td class="tdr_br">Shank only</td>
<td class="tdr_br">Each ham injected
with 10 c. c. of culture.</td>
<td class="tdr_br">19</td>
<td class="tdr_br">95</td>
</tr>
<tr>
<td class="tdr_br"> 2</td>
<td class="tdr_br">20</td>
<td class="tdr_br">12-14</td>
<td class="tdr_br">do</td>
<td class="tdr_br">do</td>
<td class="tdr_br">Not injected with culture;
check on tierce 1.</td>
<td class="tdr_br">0</td>
<td class="tdr_br">0</td>
</tr>
<tr>
<td class="tdr_br"> 3</td>
<td class="tdr_br">20</td>
<td class="tdr_br">14-16</td>
<td class="tdr_br">Regular</td>
<td class="tdr_br">Shank and body</td>
<td class="tdr_br">Each ham injected
with 10 c. c. of culture.</td>
<td class="tdr_br">9</td>
<td class="tdr_br">45</td>
</tr>
<tr>
<td class="tdr_brb"> 4</td>
<td class="tdr_brb">20</td>
<td class="tdr_brb">14-16</td>
<td class="tdr_brb">do</td>
<td class="tdr_brb">do</td>
<td class="tdr_brb">Not injected with culture;
check on tierce 3.</td>
<td class="tdr_brb">0</td>
<td class="tdr_brb">0</td>
</tr>
</table>
<p>Three hams from each tierce were selected for bacteriological and
histological examination. From tierces 1 and 3, which contained
the injected hams, three of the most pronounced “sours” were
selected from each tierce. In examining the hams bacteriologically
the following method was adopted: The hams were sectioned near
the center of the body and the larger or butt end turned up so as to
expose the cut surface. A cross section of a ham thus cut is shown
in figure 3.</p>
<p>Cultures were taken at the points indicated by the numbers and
from the exposed bone marrow of the femur by first searing the surface,
and then taking out plugs of the meat or marrow by means of
sterile instruments. The plugs of meat or marrow were dropped
into tubes containing egg-pork medium and pushed to the bottom of
the tubes by means of a sterile platinum wire. In the cultures made
from the sour hams from tierces 1 and 3, which were injected with
culture, the bacillus with which these hams were injected was found
in practically every culture, although it was sometimes absent in
the cultures taken at points near the skinned surfaces of the hams
(i. e., at points 1, 4, and 5 in fig. 3). In the cultures taken from the
meat, the bacillus was not always present in pure culture, but this is
not to be wondered at when we remember that the pickling fluids
often contain large numbers of bacteria of various kinds, and these,
of course, find their way into the hams in the pickling fluids. Especially
is this true of the hams which are pumped in the body, where
bacteria are actually pumped into the bodies of the hams in the
pumping pickle. In the case of hams which are not pumped in
the body, the pickle bacteria do not appear to penetrate the body of
the ham to any great depth.</p>
<p><span class="pagenum" id="Page_25">[Pg 25]</span></p>
<p>In figure 3 the plus signs after the figures represent the distribution
of the sour-ham bacillus in one of the hams from tierce 1, and this
may be taken as a typical example of the other sour hams which were
examined in this experiment. It should be explained that the
shaded areas are not intended to represent the actual limits of souring,
but simply the areas in which the sour odor was most pronounced
and from which it could be readily obtained with the trier. In
comparing the regular and mild cure hams, it was found that the
areas of souring as defined with the trier were more restricted in the
regular cure hams, and this was undoubtedly due to the additional
pumping which these hams received, whereby the growth of the
bacillus was partially inhibited.</p>
<div class="figcenter illowp100" id="fig3" style="max-width: 62.5em;">
<img src="images/fig3.jpg" alt=""/>
<div class="caption"><p class="hang"><span class="smcap">Fig. 3.</span>—Cross section through body of artificially soured ham, showing sour areas and points at which
cultures were taken. Darker shading indicates sour area in hams pumped in body and shank; light
shading indicates sour area in hams pumped in shank only; figures indicate points at which cultures
were taken; plus signs indicate presence of bacillus; minus sign indicates absence of bacillus; X indicates
point of inoculation.</p>
</div>
</div>
<p>It will be noticed that the sour-ham bacillus was present in cultures
taken at points outside the shaded areas, indicating that the
organism had extended generally throughout the bodies of the hams.
As the hams were inoculated at a point just to one side of and a
little behind the femur (i. e., at the point X in the figure), the presence
of the bacillus generally throughout the hams would indicate
a very extensive multiplication of the original bacilli with which the
hams were injected. In view of the fact that the bacillus in question
is nonmotile, the spread of the bacilli throughout the hams must
result simply from subdivision and growth by extension, and in
spreading throughout the hams the bacilli appear to follow along the
connective tissue bands which afford paths of least resistance. In the
cultures made from the bone marrow the bacillus was recovered in<span class="pagenum" id="Page_26">[Pg 26]</span>
pure culture from each of the hams examined, and it is probable that
the bacillus finds its way into the bone marrow from the meat by
following along the small arteries which pass through the bone. The
fact that the bacillus was found in pure culture (i. e., uncontaminated)
in the cultures made from the bone marrow is explained probably
by its capacity for growth by extension, and also by the fact that the
pickling solutions probably do not reach the bone marrow until late
in the curing and then only to a limited extent. The bacteria which
ordinarily occur in pickling fluids are not strict anaerobes and are not
placed under the most suitable conditions for growth when they
reach the interior of the ham, for it seems probable that in the interior
of hams which are totally submerged in pickling fluids the amount
of available oxygen must be extremely small. The ordinary pickle
bacteria, therefore, would not multiply as rapidly in the interior of
the hams and would not find their way into the bone marrow as
soon as would a strictly anaerobic organism.</p>
<p>Pure cultures of the sour-ham bacillus, recovered from the meat
and bone marrow of the injected hams, were compared with cultures
of the original bacillus used for inoculating the hams, and
were found to be identical. Furthermore, the bacillus with which
the hams were injected was recovered from the injected hams at
points far removed from the original point of injection, showing that
the organism had multiplied and extended throughout the bodies of
the hams and that it was clearly responsible for the souring which
the hams had undergone.</p>
<p>Sound hams from tierces 2 and 4 were examined bacteriologically
in the same manner as the injected hams, and some of the cultures
showed the ordinary pickle bacteria, but in not a single instance did
egg-pork cultures yield a sour odor, and in no case could the sour-ham
bacillus be demonstrated in any of these hams.</p>
<p>Microscopic sections and teased preparations of the muscle fibers
in salt solution were prepared from several of the sour hams in this
experiment, and these preparations showed the same histological
changes and the same distribution of bacilli as noted in the natural
sours.</p>
<p>In <a href="#Plate_III">Plate III</a>, figures 1 and 2, sections are shown of artificially soured
hams, that is, hams which were artificially soured by injections of culture;
and if these figures be compared with the sections made from
hams which had undergone spontaneous souring (see Pl. II, figs. 1 and
2) the similarity in the form and distribution of the bacilli will be at
once apparent.</p>
<p class="center small">
<span class="smcap">Bul. 132, Bureau of Animal Industry, U. S. Dept. of Agriculture. <a id="Plate_III"></a>Plate III.</span></p>
<div class="figcenter illowp80" id="pl3a" style="max-width: 50em;">
<a href="images/pl3alge.jpg">
<img src="images/pl3a.jpg" alt=""/></a>
<div class="caption"><p class="hang"><span class="smcap">Fig. 1.—Section Through Muscular Tissue of Artificially Soured
Ham, Showing Distribution of Bacilli Between the Muscle
Fibers, which are Shown in Cross Section. The Dark Lines and
Masses Between the Muscle Fibers Represent Clumps of
Bacilli.</span></p></div>
<p class="center small">(Pen-and-ink drawing made with camera lucida from section stained by
the Gram-Weigert method to show bacteria. × 85.)</p></div>
<div class="figcenter illowp80" id="pl3b" style="max-width: 50em;">
<a href="images/pl3blge.jpg">
<img src="images/pl3b.jpg" alt=""/></a>
<div class="caption"><p class="hang"><span class="smcap">Fig. 2.—Section Through Muscular Tissue of Artificially Soured
Ham, Showing Individual Bacilli Between the Muscle Fibers,
which are Cut Longitudinally.</span></p></div>
</div>
<p class="center small">(Pen-and-ink drawing made with camera lucida from section stained by
the Gram-Weigert method to show bacteria. × 320.)]</p>
<p><i>Summary and discussion of Experiment I.</i>—Comparing tierces 1
and 2, where the hams were pumped in the shank only, the only
difference being that the hams in tierce 1 were inoculated with culture
while those in tierce 2 were not, we find that in tierce 1 nineteen out
of twenty, or 95 per cent, of the hams became sour, whereas in tierce 2
all of the hams remained sweet. In view of the fact that these tierces
were held under exactly the same conditions, we must conclude that
the souring of the hams in tierce 1 was due to the injection of culture
which they received.</p>
<p>Comparing tierces 3 and 4, where the hams were pumped in both
shank and body, the hams in tierce 3 being injected with culture
while those in tierce 4 were not, we find that in tierce 3 nine out of
twenty, or 45 per cent, of the hams became sour, whereas in tierce 4 all
of the hams remained sweet. As the conditions of cure were the same
for all four tierces, we must again conclude that the souring of the
hams in tierce 3 was directly attributable to the injections of culture
which they received.</p>
<p>If now we compare tierces 1 and 3, the two tierces which were
injected with culture, we find that in the case of tierce 1, where the
hams were pumped in the shank only, 95 per cent became sour;
whereas in the case of tierce 3, where the hams were pumped in both
shank and body, only 45 per cent became sour. In other words, the
percentage of souring in those hams which were pumped in the body
as well as in the shank was 50 percent less than in those hams which
were pumped in the shank only. Inasmuch as the only difference
in the treatment accorded tierces 1 and 3 lay in the additional
pumping given the hams in tierce 3, we must conclude that the
marked diminution in the percentage of souring in the case of tierce
3 was undoubtedly due to the additional pumping which these hams
received, the hams being saturated at the start with the pumping
pickle. It will be shown later that both sodium chlorid and potassium
nitrate exert an inhibitory effect upon the bacillus with which the
hams were injected, which directly bears out the foregoing conclusion.</p>
<p>In tierces 2 and 4, the two check tierces which were not injected
with culture, all of the hams were sweet at the end of the cure, showing
that the conditions under which the experiment was carried out were
entirely favorable to a successful cure.</p>
<p>The sour odor obtained from the artificially soured hams in this
experiment was pronounced by the meat inspector who tested the
hams, and who was entirely unaware of the treatment they had
received, to be identical with the usual sour odor which characterizes
hams that have undergone spontaneous souring; in other words,
there was no difference in odor between these artificially soured hams
and natural sours.</p>
<p>With regard to the variation in the degree and the extent of the
souring exhibited by the individual hams in the two inoculated
tierces, where some of the hams showed pronounced souring throughout
the body and shank, while others which had been injected with
the same amount of culture showed only slight souring in the body,<span class="pagenum" id="Page_28">[Pg 28]</span>
several factors must be considered, viz:(1) Differences in the reaction
of the meat of the individual hams which may have exerted an influence
on the growth of the bacteria with which the hams were injected.
(2) Variations in the texture of the muscle fibers and connective
tissue of the individual hams, permitting in some cases a more rapid
and thorough penetration of the pickling fluids to the interior of the
hams, whereby the inhibitory effect of the sodium chlorid and the
potassium nitrate on the bacteria would come into play earlier.
(3) Variations in pumping, whereby more of the pickling solution was
forced into some of the hams than into others. Probably all three of
these factors would have to be taken into account in explaining the
variation in the degree and extent of the souring exhibited by the
injected hams.</p>
<p>With regard to the souring of the bone marrow, we find that of
nineteen sour hams in tierce 1 eighteen showed sour marrows, while
in tierce 3 nine sour hams showed seven sour marrows. The high
proportion of marrow sours is not surprising when it is recalled that
of the nineteen sour hams in tierce 1 the meat was markedly sour in
sixteen, while of the nine sour hams in tierce 3 the meat was markedly
sour in five. In the case of the four sour hams in tierce 3
which showed slight souring in the body, two of these showed sour
marrows, while in two the marrows were sweet. In this experiment
the percentage of sour hams showing sour marrows corresponds
with the percentage of marrow-sour hams found in the packing
house, where, as has been pointed out before, a ham which is markedly
sour in the body will practically always show sour marrow,
while in hams which show only slight souring in the body the marrow
is involved in about 50 per cent of the cases.</p>
<h6><i>Experiment II.</i></h6>
<p>This experiment was essentially a repetition of Experiment I, but
was carried out at a different packing establishment and under somewhat
different conditions.</p>
<p>Two lots of hams were injected with a culture suspension of the
bacillus at different stages of the cure, or rather at different stages in
the preparation for cure, i. e.,(1) on the hanging floor, previous to
chilling, and (2) after chilling and pumping and immediately before
packing. Three tierces, each containing 20 hams, were put down.
Two of the tierces contained the hams injected with culture, while
the third tierce contained check hams which had not been treated
with culture. Half of the hams in each tierce were pumped
in the shank, while the other half were pumped in both body and
shank. The same pumping and curing pickles were used for all three
tierces, and were the regular pumping and regular curing pickles of
the establishment at which the experiment was carried out. The<span class="pagenum" id="Page_29">[Pg 29]</span>
hams used were all 14 to 16 pounds in weight and were subjected to
the usual 48-hour chill with an additional chill of 48 hours after they
were cut from the carcass. They were packed in tierces which had
been thoroughly scrubbed and cleaned with boiling water. The
tierces were held in a pickling room at a temperature of 33° to 36° F.,
the temperature never rising above 36° F., and were rolled three
times during the curing period. The hams were in cure for about
eighty days. At the end of the cure the hams were carefully tested by
a trained meat inspector, who knew nothing of the treatment they
had received.</p>
<p>The culture suspension was prepared from 20 tubes of egg-pork
medium in the same manner as that used in Experiment I, the cultures
being diluted with sufficient salt solution to give 400 cubic centimeters
of suspension. The cultures from which the suspension was prepared
had grown at room temperature for ten days. The suspension was
examined microscopically and showed large numbers of the bacilli in
the form of filaments or long chains, with many of the individual
organisms showing large terminal spores. The hams were injected
with the culture suspension in the same manner as those in Experiment
I.</p>
<p>The details of the experiment were as follows:</p>
<div class="blockquot">
<p><i>Tierce No. 1.</i>—Contained 20 hams, each ham being injected with 20 cubic centimeters
of the suspension or the equivalent of 10 cubic centimeters of the original
culture. The hams were injected while on the hanging floor, before they had been
cut from the carcasses and previous to chilling. The carcasses were still quite warm—that
is, had lost but little of their body heat when the injections were made. The
carcasses, which had been carefully tagged, were then run into coolers and given
the usual 48-hour chill, after which the hams were severed from the carcasses and
given an additional 48-hour chill in accordance with the custom of the packing
house at which the experiment was carried out. The hams were next pumped with
regular pumping pickle, 10 being pumped in both body and shank and 10 in shank
only. They were finally packed in a tierce, which was then headed up, filled with
regular curing pickle, and placed in cure.</p>
<p>Result: When tested at the end of the cure it was found that the 10 hams which
were pumped in the shank only were all sour. In each of them the souring extended
throughout the entire ham, in the shank as well as in the body, and was very pronounced,
so much so that they were characterized as “stinkers” by the meat inspector
who assisted in testing them. The bone marrow of the femur or middle bone was
sour in all of these hams. Of the 10 hams which were pumped in both body and
shank 7 showed well-marked souring throughout the body, but the souring did not
extend into the shank. The bone marrow of the femur was found to be sour in 6 of
these hams, while in 1 the souring had not extended through to the bone marrow.</p>
<p><i>Tierce No. 2.</i>—Contained 20 hams which were chilled and pumped in exactly the
same manner as those in tierce No. 1. These hams were injected with culture after
they had been chilled and pumped, or just before they were placed in cure. The
hams in this tierce, therefore, were injected with culture four days later than those
in tierce 1. The hams were injected with a bacterial suspension prepared in the
same manner as that used for tierce 1, except that the egg-pork cultures from which
the suspension was prepared were 7 days instead of 10 days old. Each ham was<span class="pagenum" id="Page_30">[Pg 30]</span>
injected with 20 cubic centimeters of the suspension or the equivalent of 10 cubic
centimeters of the original culture. The hams were injected in the same manner as
those in tierce 1.</p>
<p>Result: When tested at the end of the cure, it was found that of the 10 hams which
were pumped in the shank all were sour; in 8 of these the souring was very marked
throughout the body of the ham and extended into the shank; in all of these hams
the souring had extended through to the bone marrow of the middle bone or femur.
Of the 10 hams which were pumped in both body and shank 6 were sour in the body.
These hams were classed by the meat inspector who examined them as “light body
sours,” and in none of them did the souring extend into the shank or through the
bone into the bone marrow of the femur.</p>
<p><i>Tierce No. 3.</i>—Contained 20 hams which were chilled and pumped in the same
manner as those in the two preceding tierces. These hams were not injected with
culture and were put down to serve as checks on the cure. In other words, they
were pumped with the same pickling fluids, were subjected to exactly the same cure,
and were held under precisely the same conditions as those in the preceding tierces,
the only difference being that the hams in this tierce were not injected with culture.</p>
<p>Result: When tested at the end of the cure, all of the hams in this tierce were found
to be perfectly sound and sweet.</p>
</div>
<p class="center"><i>Results of Experiment II.</i></p>
<table class="standard" summary="">
<tr>
<th class="tdc brdr" rowspan="2">No. of tierce.</th>
<th class="tdc brdr" rowspan="2">Number of hams.</th>
<th class="tdc brdr" rowspan="2">Average weight<br />of hams.<br /><i>Pounds.</i></th>
<th class="tdc brdr" rowspan="2">How pumped.</th>
<th class="tdc brdr" rowspan="2">Treatment.</th>
<th class="tdc brdr" colspan="2">Condition at end of cure.</th>
</tr>
<tr>
<th class="tdc brdr">Number of<br />sour hams.</th>
<th class="tdc brdr">Percentage of<br />sour hams.</th>
</tr>
<tr>
<td class="tdr_br" rowspan="2">1</td>
<td class="tdr_br" rowspan="2">20</td>
<td class="tdr_br" rowspan="2">14-16</td>
<td class="tdl_br">10 in shank</td>
<td class="tdl_br">Each ham injected with 20
c. c. of culture prior to chilling and pumping.</td>
<td class="tdr_br">10</td>
<td class="tdr_br">100</td>
</tr>
<tr>
<td class="tdl_br">10 in body and shank</td>
<td class="tdc_br">do</td>
<td class="tdr_br">7</td>
<td class="tdr_br">70</td>
</tr>
<tr>
<td class="tdr_brtd" rowspan="2">2</td>
<td class="tdr_brtd" rowspan="2">20</td>
<td class="tdr_brtd" rowspan="2">14-16</td>
<td class="tdl_brtd">10 in shank</td>
<td class="tdl_brtd">Each ham injected with 20
c. c. of culture subsequent to chilling and pumping.</td>
<td class="tdr_brtd">10</td>
<td class="tdr_brtd">100</td>
</tr>
<tr>
<td class="tdl_br">10 in body and shank</td>
<td class="tdc_br">do</td>
<td class="tdr_br">6</td>
<td class="tdr_br">60</td>
</tr>
<tr>
<td class="tdr_brtd" rowspan="2">3</td>
<td class="tdr_brtd" rowspan="2">20</td>
<td class="tdr_brtd" rowspan="2">14-16</td>
<td class="tdl_brtd">10 in shank</td>
<td class="tdl_brtd">Not injected with culture</td>
<td class="tdr_brtd">0</td>
<td class="tdr_brtd">0</td>
</tr>
<tr>
<td class="tdl_brb">10 in body and shank</td>
<td class="tdc_brb">do</td>
<td class="tdr_brb">0</td>
<td class="tdr_brb">0</td>
</tr>
</table>
<p>Four hams were selected from each tierce for bacteriological and
histological examination. From tierces 1 and 2, in which the hams
were injected with culture, 4 of the sourest hams were selected from
each tierce. Cultures were made from these hams in the same
manner as described under Experiment I and with the same result—that
is, the sour-ham bacillus was found throughout the bodies of
the hams. Microscopic sections were also prepared from these hams
and showed the same histological changes and the same distribution
of bacilli as noted for the hams in Experiment I.</p>
<p><i>Summary and discussion of Experiment II.</i>—Comparing tierces 1
and 2, in which the hams were injected with culture, with tierce 3,
where the hams were not injected with culture, we find that in tierce
1 seventeen hams (85 per cent) became sour and in tierce 2 sixteen
hams (80 per cent) became sour, whereas in tierce 3 all of the hams<span class="pagenum" id="Page_31">[Pg 31]</span>
were sweet. The fact that all of the hams in tierce 3, the check
tierce, were sweet indicates that the conditions were favorable for a
successful cure; and as all three tierces were cured under exactly the
same conditions, the only difference being that the hams in tierces
1 and 2 were injected with culture, whereas those in tierce 3 were not
injected with culture, we must conclude that the souring of the hams
in tierces 1 and 2 was due to the injections of culture which they
received.</p>
<p>Comparing tierce 1 with tierce 2, we find that the hams in tierce 1
showed more extensive souring than did those in tierce 2, this being
especially noticeable in the case of the hams which were pumped in
both body and shank. This difference in the extent or degree of souring
was probably due to the fact that the hams in tierce 1 were
injected while they were still warm and before they had lost their
animal heat, the bacterial suspension thus having a better chance to
become disseminated through the meat. The hams in tierce 2 were
injected with culture after they had been chilled, when the tissues
were more or less contracted and the conditions less favorable for the
dissemination of the suspension throughout the meat. The hams in
tierce 1 were also injected four days earlier than those in tierce 2,
and prior to pumping; and this would explain the greater difference
in the extent of the souring in the case of the hams which were
pumped in both body and shank, as in tierce 1 the bacteria had four
days in which to develop before coming in contact with the pickling
fluids, whereas in tierce 2 the bacteria were injected after the hams
were pumped with pickle and were thus brought into immediate
contact with the pickling fluids, which, as will be shown later, have a
distinct inhibitory action upon the bacillus in question. In the case
of the hams which were pumped in the shank but not in the body
there was not this difference, as in these hams the pickling fluids
must penetrate into the bodies of the hams from the outside. As it
requires some time for the pickling fluids to reach the interior of a
ham, the bacteria were thus afforded quite an interval in which to
develop before being exposed to the inhibitory action of the pickling
fluids. A chemical study of the processes involved in ham curing
has been carried out in the Biochemic Division and the approximate
rate of penetration of the curing pickle determined, and it was found
that it required about four weeks for the interior of a 10-pound ham
which had not been pumped to acquire its maximum percentage of
sodium chlorid.</p>
<p>To recapitulate: In this experiment 40 hams were injected with
culture, half of this number being pumped in the shank only and
half in both body and shank. Of the 20 which were pumped in the
shank only, every ham without exception, or 100 per cent, became
sour. Of those which were pumped in both body and shank, 13, or<span class="pagenum" id="Page_32">[Pg 32]</span>
65 per cent, became sour. The reduction in the percentage of sours
in the last lot was clearly due to the additional pumping which these
hams received.</p>
<p>If now we compare tierce 2 in this experiment with tierces 1 and 3
in Experiment I—these three tierces being comparable, as they were
all injected with culture at the same stage in their preparation for
cure, that is, subsequent to chilling and pumping—we find, in the
case of the hams pumped in both body and shank, 65 per cent of
sours in Experiment II as against 45 per cent in Experiment I, and
this difference is undoubtedly due to the heavier dose of culture
used in Experiment II, where the hams were given the equivalent
of 10 cubic centimeters of egg-pork culture as against 2-1/2 cubic centimeters
in Experiment I. In the case of the hams which were
pumped in the shank but not in the body, the percentage of sours
was practically the same in the two experiments—in Experiment I
all but one of these hams became sour, while in Experiment II all of
them became sour. The degree or extent of the souring in these last
hams, however, was greater in Experiment II, a result of the heavier
injections of culture which they received.</p>
<h6><i>Summary of Experiments I and II.</i></h6>
<p>Summarizing the results obtained in Experiments I and II, we find
that culture suspensions of the anaerobic bacillus isolated from sour
hams caused souring with great uniformity when injected into the
bodies of sound hams which were pumped in the shank only. In
the two experiments, 40 sound hams which were pumped in the
shank only were injected with culture suspensions of the bacillus,
with the result that 39, or 97.5 per cent, became sour during the
process of cure; and it is quite probable, as we have pointed out
before, that one of these hams was overlooked in making the inoculations,
otherwise the entire lot would have become sour.</p>
<p>The inhibitory action of the pickling fluids upon the bacillus is
well shown in the case of those hams which were pumped in both
body and shank. Out of 40 hams which were pumped in both body
and shank, 22, or 55 per cent, became sour in the process of curing.
Inasmuch as these hams were cured under precisely the same conditions
as the hams which were pumped in the shank only, we must
conclude that the diminution in souring in these hams was undoubtedly
due to the additional pumping which they received, whereby
the bacteria with which these hams were injected were brought into
immediate contact with the strong pumping pickle and their development
thereby inhibited.</p>
<p>In these two experiments it was proven beyond doubt that the
anaerobic bacillus isolated from sour hams was capable of producing<span class="pagenum" id="Page_33">[Pg 33]</span>
souring when introduced into the bodies of sound hams; and in view
of the fact that this bacillus was constantly present in hams which
had undergone spontaneous or natural souring, and was the only
organism that could be isolated from such hams that was capable of
producing in egg-pork cultures the characteristic sour-ham odor, the
conclusion seems justifiable that this bacillus is an undoubted cause
of the ham souring which occurs in the packing house; and the
results thus far obtained indicate that it is an important, if not the
only, factor concerned in ham souring.</p>
<p>Having established the etiological relation of the bacillus isolated
from sour hams with ham souring, the next point to be considered
was the manner in which this bacillus finds its way into the bodies of
the hams.</p>
<h3>PROBABLE METHOD BY WHICH HAM-SOURING BACILLUS ENTERS HAMS.</h3>
<p>Regarding the question of the probable method by which the ham-souring
bacillus enters hams, there were three possibilities to be taken
into consideration:(1) That the bacillus is present in the flesh of
hogs at the time of slaughter,(2) that the bacillus gains entrance
through the pickling fluids,(3) that the bacillus is introduced into
the bodies of the hams in the handling or manipulation which the
hams undergo in preparation for, or during, the process of curing.</p>
<h4><span class="smcap">Possibility of Infection Prior to Slaughter.</span></h4>
<p>In order to throw some light upon this point, a number of fresh
hams—that is, hams which had been chilled but not pumped or subjected
to any other manipulation—were examined bacteriologically,
but in no case could the anaerobic bacillus which was isolated from
sour hams be detected in any of them. The fact that in certain
of the smaller packing establishments which cure their hams without
pumping the percentage of souring is extremely low would also
seem to negative this possibility, for if the bacillus which causes
souring were present in the hams at the time of slaughter, sour hams
would be as frequent at such establishments as at those establishments
which make a practice of pumping. Furthermore, a laboratory
study, biological and chemical, of the bacillus isolated from
sour hams shows that this organism belongs to the class of putrefactive
bacteria, and while such bacteria may be present in the
intestines of healthy animals, as, for example, the bacillus of Bienstock
(<i>Bacillus putrificus</i>), these bacteria do not invade the organs
and tissues of the body until after the death of the animal, and the
packing-house practice of rapidly eviscerating the hogs immediately
after slaughter would certainly preclude this possibility.</p>
<p><span class="pagenum" id="Page_34">[Pg 34]</span></p>
<h4><span class="smcap">Possible Infection from Pickling Fluids.</span></h4>
<p>With regard to the second possibility, that the bacillus finds its
way into the hams in the curing pickles, it was determined by laboratory
experiment that the addition of 3 per cent of sodium chlorid or
3 per cent of potassium nitrate to laboratory media completely
inhibits the growth of the bacillus. As the pickling solutions always
contain considerably more than these percentages of sodium chlorid
and potassium nitrate, it would be impossible for the bacillus to
multiply in the pickles. Additional laboratory experiments demonstrated,
however, that the bacillus or its spores may remain alive in
the curing pickles for at least thirty days, and it seemed possible that
the curing pickles might become contaminated at times with the
bacilli, and that the bacilli, although incapable of multiplying in the
pickles, might find their way into the bodies of the hams in the
pickling fluids. In order to throw some light upon this point, the
following experiment was carried out:</p>
<h5>EXPERIMENT TO SHOW WHETHER INFECTION TAKES PLACE FROM THE CURING PICKLE.</h5>
<p>In this experiment two tierces were put down, each containing
20 hams. The hams weighed from 14 to 16 pounds and had received
the usual 48-hour chilling. The pickling solutions employed were
the regular curing pickles of the establishment at which the experiment
was carried out. The curing pickle in one tierce was inoculated
with 400 cubic centimeters of a culture suspension of the bacillus,
prepared in the same manner as that used for the injection of the
hams in tierce 2 in Experiment II. A microscopic preparation made
from a small drop of the culture suspension before adding it to the
pickle showed the bacilli in large numbers, and in the 400 cubic
centimeters of the suspension there were millions of the bacteria.
The curing pickle in the other tierce was left untreated, the hams
in this tierce serving as a check. The tierces used in this experiment,
as in all of the experiments, were thoroughly cleaned with boiling
water before the hams were placed in them. The experiment was
conducted in a pickling room which was held at 33° to 36° F., and
the tierces were rolled three times during the cure. The details of
the experiment are as follows:</p>
<div class="blockquot">
<p><i>Tierce 1.</i>—Contained 20 hams, half of which were pumped in both body and shank
and half in the shank only. As soon as they were pumped the hams were packed in
the tierce. Sufficient curing pickle to fill the tierce was then measured out in a clean
barrel and to it was added the culture suspension. The culture was thoroughly mixed
with the pickle and the latter was then run into the tierce containing the hams.</p>
<p>Result: When tested at the end of the cure, two of the hams which had been
pumped in the shank only showed slight souring in the body. The rest of the hams
were sweet.</p>
<p><i>Tierce 2.</i>—Contained 20 hams which were pumped in the same manner as those in
tierce 1. The curing pickle was the same as that used for tierce 1, but without the<span class="pagenum" id="Page_35">[Pg 35]</span>
addition of culture. This tierce was put down as a check on tierce 1, the hams being
cured under exactly the same conditions, but without the addition of culture to the
curing pickle.</p>
<p>Result: One of the hams which was pumped in the shank only developed slight
souring in the body. The remainder of the hams were sweet.</p>
</div>
<p>Comparing tierce 1, which contained the inoculated pickle, with
tierce 2, the check tierce which contained uninoculated pickle, we
find there was practically no difference in the final result. In tierce
1 two of the hams developed slight souring, while in tierce 2 one of
the hams became slightly sour. All of these hams had been pumped
in the shank only. The fact that one of the hams in the check tierce
developed slight souring was undoubtedly due to bacterial contamination
in pumping or in the handling which the hams underwent prior
to pickling, and the slight souring of the two hams in tierce 1 must
also be attributed to the same cause or causes, for had the souring
in these last hams resulted from the penetration of the bacteria from
the pickling solution a higher percentage should have become sour.
Furthermore, if the souring of the two hams in tierce 1 had resulted
from the penetration of the bacteria from the curing pickle, the souring
should have been general throughout the bodies of these hams,
whereas the souring was only evident around the bone and was slight
in degree.</p>
<p>From this experiment the conclusion would seem justified that the
bacillus which causes ham souring does not usually find its way into
the bodies of the hams from the curing pickle, although it would be
going too far, perhaps, to say that infection never takes place from
the curing pickle. The experiment, however, indicates clearly that
the curing pickles are certainly not the main channel through which
the hams become infected. In referring to the curing pickles, it
should be understood that we refer here to the pickling solutions in
which the hams are immersed, and not to the pumping pickles. The
possibility of infection through the pumping pickle will be discussed
later.</p>
<h4><span class="smcap">Possible Infection through Manipulation or Handling.</span></h4>
<p>There are at least three possible ways in which hams may become
infected from the handling which they receive in preparation for, or
during the process of curing, viz: From the thermometers used in
taking the inside temperatures of the hams, from the pumping
needles, and from the billhooks used in lifting the hams.</p>
<h5>INFECTION FROM HAM THERMOMETERS.</h5>
<div class="figleft illowp20" id="fig4" style="max-width: 9.375em;">
<img class="w100" src="images/fig4.jpg" alt=""/>
<div class="caption"><p class="hang"><span class="smcap">Fig. 4.</span>—Diagrammatic views showing
construction of ham thermometer. A, front view, showing open space
between metal point and mercury bulb, which becomes filled with
particles of meat, grease, and dirt; B, side view.</p></div>
</div>
<p>The packing-house method of taking the temperatures of hams by
means of a pointed, metal-capped thermometer which is thrust deep
into the bodies of the hams has already been referred to, but deserves
to be described somewhat more in detail, as it will be at once apparent<span class="pagenum" id="Page_36">[Pg 36]</span>
that this manipulation furnishes a ready means
whereby hams may become infected with putrefactive
bacteria. The construction of a ham thermometer
is shown in figure 4.</p>
<p>The instrument consists of a glass thermometer
inclosed in a metal case, the front portions of the
case being cut away so as to expose the scale above
and the mercury bulb below. As was explained
before, the thermometer is thrust deep into the
body of the ham so that the pointed end containing
the mercury bulb rests beside or a little behind
the upper portion of the femur, the bone being
used as a guide in introducing the thermometer.</p>
<p>Ham temperatures are taken at three stages in
the preparation for cure—(1) on the hanging floor,
just before the hams go to the chill rooms, in order
to determine the amount of heat lost prior to chilling;
(2) on leaving the chill rooms, in order to determine
the thoroughness of the chill;(3) on the
packing floor, just before the hams are placed in
pickle, as a further check on the thoroughness of
the chilling.</p>
<p>In taking the temperatures of hams which have
been chilled—and most of the temperatures are
taken subsequent to chilling—it is customary for
the packing-house attendant who has this matter
in charge to warm the thermometer by holding the
pointed or bulb end in his hand, so as to force the
mercury column up to about 60° F., or well above
the temperature of hams. The thermometer is
then thrust into the ham and allowed to remain
for several minutes, by which time the mercury
column will have fallen to the temperature of the
ham. The thermometer is then slowly withdrawn
so as to expose the top of the mercury column, and
an accurate reading is thus obtained of the inside
temperature of the ham. The thermometer is
warmed by the hand before each ham is tested, and
this undoubtedly insures more accurate readings
than would result were the thermometer removed
from one ham and plunged immediately into
another, but the procedure is open to certain
objections, for the open space between the
metal point of the thermometer and the mercury<span class="pagenum" id="Page_37">[Pg 37]</span>
bulb soon becomes filled with particles of meat and with grease and
dirt from the attendant’s hands, and it is at once apparent that a
thermometer in this condition would furnish a ready means whereby
extraneous matter might be introduced into the bodies of the hams.
In other words, a contaminated thermometer would furnish an excellent
means whereby hams could be inoculated with putrefactive
bacteria.</p>
<p>In order to determine whether hams actually become inoculated in
this manner, the following experiment was carried out:</p>
<h5>EXPERIMENT TO SHOW WHETHER HAMS BECOME INFECTED FROM HAM THERMOMETERS.</h5>
<p>This experiment was designed to show (1) whether the usual
packing-house method of taking ham temperatures was apt to induce
souring in the hams thus tested, and (2) whether souring would result
in hams which were tested with a thermometer purposely contaminated
with the bacillus isolated from sour hams.</p>
<p>The experiment was carried out as follows: Thirty hog carcasses
were selected as they entered the hanging floor from the killing floor.
They had been cleaned, eviscerated, and split, and were of the same
average weight and of sufficient size to yield hams weighing from 12
to 14 pounds. They were divided into three lots of 10 each and were
allowed to remain on the hanging floor for two hours, after which they
were given the usual 48-hour chilling.</p>
<div class="blockquot">
<p><i>Lot 1.</i>—The hams in this lot were tested with an ordinary ham thermometer as they
entered the hanging floor, as they left the hanging floor, and as they left the coolers.
The thermometer used was borrowed from one of the plant attendants and was used in
the condition in which it was received from him; that is, it was not cleaned or disinfected
prior to use.</p>
<p><i>Lot 2.</i>—The hams in this lot were tested as they entered the hanging floor with a
thermometer which had been previously cleaned and disinfected and then dipped in
a culture suspension of the meat-souring bacillus which was isolated from sour hams.
The thermometer was dipped in the culture suspension before each ham was tested.
No further temperatures were taken of these hams. The thermometer was carefully
cleaned and disinfected before it was returned to the attendant from whom it was
borrowed.</p>
<p><i>Lot 3.</i>—The hams in this lot were not tested at all, and were intended as checks on
the cure.</p>
</div>
<p>The three lots of carcasses were carefully tagged and were chilled in
a special cooler to themselves. Upon leaving the cooler the hams
were cut from the carcasses and trimmed. The three lots of hams
were then cured in separate tierces. All of the hams were subjected to
exactly the same cure.</p>
<p>The pickles used were the regular pumping and regular curing
pickles of the establishment at which the experiment was carried out.</p>
<p><span class="pagenum" id="Page_38">[Pg 38]</span></p>
<p>The hams in lot 3 were pumped first and those in lot 1 were
pumped next. The needle was then removed and a fresh, clean
needle was used for lot 2. This was done in order to prevent the
possibility of carrying over bacteria from one lot of hams to another
on the pumping needle. The tierces were thoroughly cleaned with
boiling water before being used. The curing was carried out in a
pickling cellar which was held at 33° to 36° F., the temperature never
rising above the latter figure. The tierces were rolled three times
during the curing. The details and results were as follows:</p>
<div class="blockquot">
<p><i>Tierce 1.</i>—Contained 20 hams, half of which were pumped in both body and shank
and half in the shank only. These hams were taken from the carcasses in lot 1 and had
been tested several times with a ham thermometer, as already described.</p>
<p>Result: At the end of the cure it was found that of the 10 hams which were pumped
in the shank, 5 showed well-marked souring in the body, while of the 10 hams which
were pumped in both body and shank, 2 showed slight souring in the body.</p>
<p><i>Tierce 2.</i>—Contained 20 hams, which were pumped in the same manner as those in
tierce 1. These hams were taken from the carcasses in lot 2 and had been tested once
with a thermometer which was dipped in a culture suspension of the bacillus isolated
from sour hams.</p>
<p>Result: The 10 hams which were pumped in the shank only all became sour. When
they were tried out at the end of the cure, they showed pronounced souring throughout
the entire body and were classed as “stinkers” by the meat inspector who examined
them. The souring extended through to the bone marrow of the femur in all of these
hams. Of the 10 hams which were pumped in both body and shank, 7 showed
well-marked souring in the body, but not as pronounced as in those pumped in the
shank only; in five of these hams the souring extended through to the bone marrow of
the femur, while in 2 the bone marrow remained sweet.</p>
<p><i>Tierce 3.</i>—Contained 20 hams, which were pumped in the same manner as those in
the two preceding tierces. These hams were not tested with a thermometer, and were
put down as a check on the cure. They were pumped with the same pumping pickle,
subjected to the same cure, and held under precisely the same conditions as the hams
in the two preceding tierces.</p>
<p>Result: When tested at the end of the cure, all of these hams were found to be
perfectly sound and sweet.</p>
</div>
<p class="center"><i>Results of experiment to show whether hams become infected from ham thermometers.</i></p>
<table class="standard" summary="">
<tr>
<th class="tdc brdr" rowspan="2">No. of tierce.</th>
<th class="tdc brdr" rowspan="2">Number of hams.</th>
<th class="tdc brdr" rowspan="2">Average weight of hams.<br /><i>Pounds.</i></th>
<th class="tdc brdr" rowspan="2">How pumped.</th>
<th class="tdc brdr" rowspan="2">Treatment.</th>
<th class="tdc brdr" colspan="2">Condition at end of cure.</th>
</tr>
<tr>
<th class="tdc brdr">Number of sour hams.</th>
<th class="tdc brdr">Percentage of sour hams.</th>
</tr>
<tr>
<td class="tdr_br" rowspan="2">1</td>
<td class="tdr_br" rowspan="2">20</td>
<td class="tdr_br" rowspan="2">12-14</td>
<td class="tdl_br">10 in shank</td>
<td class="tdl_br">Tested in several stages in preparation for cure
which had not been cleaned.</td>
<td class="tdr_br">5</td>
<td class="tdr_br">50</td>
</tr>
<tr>
<td class="tdl_br">10 in body and shank</td>
<td class="tdc_br">do</td>
<td class="tdr_br">2</td>
<td class="tdr_br">20</td>
</tr>
<tr>
<td class="tdr_br" rowspan="2">2</td>
<td class="tdr_br" rowspan="2">20</td>
<td class="tdr_br" rowspan="2">14-16</td>
<td class="tdl_br">10 in shank</td>
<td class="tdl_br">Tested once with ham thermometer dipped
in culture suspension of anaerobic bacillus isolated
from sour hams.</td>
<td class="tdr_br">10</td>
<td class="tdr_br">100</td>
</tr>
<tr>
<td class="tdl_br">10 in body and shank</td>
<td class="tdc_br">do</td>
<td class="tdr_br">7</td>
<td class="tdr_br">70</td>
</tr>
<tr>
<td class="tdr_brb" rowspan="2">3</td>
<td class="tdr_brb" rowspan="2">20</td>
<td class="tdr_brb" rowspan="2">14-16</td>
<td class="tdl_br">10 in shank</td>
<td class="tdl_br">Not tested with thermometer.</td>
<td class="tdr_br">0</td>
<td class="tdr_br">0</td>
</tr>
<tr>
<td class="tdl_brb">10 in body and shank</td>
<td class="tdc_brb">do</td>
<td class="tdr_brb">0</td>
<td class="tdr_brb">0</td>
</tr>
</table>
<p><span class="pagenum" id="Page_39">[Pg 39]</span></p>
<p>Several hams from each tierce were examined bacteriologically.
cultures being taken from the meat near the bone and from the bone
marrow of the femur.</p>
<p>In the sour hams from tierce 1 cultures taken from the meat near
the bone showed the same anaerobic bacillus noted in other sour
hams (i. e., the same bacillus which caused souring in Experiments I
and II), but these cultures were contaminated with other bacteria
which were probably introduced on the thermometer along with the
ham-souring bacillus. None of the contaminating bacteria were
capable, however, of producing a sour-meat odor when grown on the
egg-pork medium. Pure cultures of the ham-souring bacillus were
obtained from the bone marrow of some of these hams, showing that
this bacillus had penetrated through to the bone marrow while the
other bacteria had not.</p>
<p>From the sour hams in tierce 2 the ham-souring bacillus was
recovered readily, and often in pure culture, from the hams which
had been pumped in the shank only, whereas it was usually contaminated
with pickle bacteria in the hams which had been pumped
in both body and shank.</p>
<p>In the case of the sound hams in tierce 3, cultures taken from the
meat near the bone and from the bone marrow of the femur were
negative in the hams which had been pumped in the shank only,
while cultures taken from corresponding points in the hams pumped
in both body and shank showed ordinary pickle bacteria, which had
evidently been introduced into the bodies of these hams in the pumping
pickles. None of these hams exhibited the slightest sour odor.</p>
<p><i>Summary of experiment.</i>—In this experiment 20 hams (tierce 1)
were tested with an ordinary ham thermometer in the usual packing-house
manner. Half of these hams were subjected to the mild cure
and half were given the regular cure, with the result that 50 per cent
of those receiving the mild cure and 20 per cent of those receiving the
regular cure became sour.</p>
<p>A second lot of 20 hams (tierce 2) were tested with a thermometer
which had been purposely contaminated with a culture suspension of
the ham-souring bacillus. These hams were cured in the same manner
as the first lot, with the result that all of those receiving the mild
cure and 70 per cent of those receiving the regular cure became sour.</p>
<p>A third lot of 20 hams (tierce 3) which had not been tested at all
were cured in the same manner as the two preceding lots, as a check
on the cure. All of these hams were sweet at the end of the cure.</p>
<p>Inasmuch as the three lots of hams were cured under precisely the
same conditions and were handled in the same manner prior to pickling,
the only difference being that the hams in tierces 1 and 2 were
tested with the ham thermometer while those in tierce 3 were not,
we must conclude that the souring of the hams in tierces 1 and 2<span class="pagenum" id="Page_40">[Pg 40]</span>
resulted from the testing which these hams received. In the case
of tierce 1 the hams became infected from a thermometer which, in
the ordinary routine use of the packing house, had become accidentally
contaminated with the ham-souring bacillus. In the case
of tierce 2 the hams became infected from a thermometer which
had been artificially contaminated with the bacillus. The high
percentage of sours in this last lot is due to the fact that these
hams were heavily infected with the ham-souring bacillus, for owing
to the construction of the ham thermometer many thousands of the
bacilli were unquestionably introduced into each ham on the point
of the thermometer. In the ordinary routine of ham testing, where
hams become infected from foreign matter introduced on the thermometer,
the percentage of souring, as shown in tierce 1, would be
less, for it is not to be supposed that ham thermometers are always
contaminated with the ham-souring bacillus, but that they only
become so at times, and that probably only a few of the bacilli
are then introduced.</p>
<p>This experiment, we think, proves conclusively (1) that the ham-souring
bacillus may be introduced into the bodies of hams on the
thermometers used in testing the hams, and (2) that the packing-house
method of taking ham temperatures by means of a thermometer
which is thrust deep into the bodies of the hams may cause souring
in the hams thus tested.</p>
<p>As a further proof that hams may become contaminated in this
manner, a series of cultures were made from scrapings taken from
ham thermometers. The scrapings consisted of the accumulations
of bits of meat, grease, and dirt that collect on the thermometers,
and were taken from the thermometers while the latter were in
ordinary routine use in the packing house. In a series of six cultures
which were made from such scrapings at different times, the same
bacillus which was isolated from sour hams and shown to cause meat
souring was found three times. In other words, the ham-souring
bacillus was present in 50 per cent of the cultures made from thermometer
scrapings, and many hams undoubtedly become infected
from the thermometers. Souring would be almost certain to result
in mild-cure hams if these hams were tested with a thermometer
which had become accidentally contaminated with the ham-souring
bacillus, as the bacillus would have time to develop within the bodies
of the hams before being inhibited by the curing pickle, which penetrates
slowly into the bodies of these hams. In the case of regular
cure hams—that is, hams which are pumped in both body and shank—souring
would be much less apt to occur after the use of a contaminated
thermometer, as these hams are more or less saturated with a
strong pumping pickle at the beginning of the cure, which would
tend to inhibit the growth of any bacteria that might be introduced
on the thermometers.</p>
<p><span class="pagenum" id="Page_41">[Pg 41]</span></p>
<p>The fact that souring may result in hams from the use of a contaminated
thermometer would explain the occurrence of several sours in
one vat, for in testing hams just before they go into cure several hams
are usually tested in succession, and these would in all likelihood go
into the same vat. Supposing the thermometer to have been contaminated
with the ham-souring bacillus at the time these hams were
tested, this would explain a fact which has been often noted, namely,
the occurrence of several sours in one vat while other vats containing
the same run of hams show no sours.</p>
<p>If souring resulted in all of the hams which are subjected to a thermometer
test in the daily routine of the packing house, this manipulation
alone might account for nearly all of the sours which occur, but
the experiment which has been just described shows that all of these
hams do not become sour. In tierce 1, where each ham was subjected
to three thermometer tests at different times, souring resulted in 35
percent (this includes both mild and regular cure) of the hams thus
tested, and in actual practice the percentage of sours in hams which
have been subjected to the thermometer test would probably be
somewhat less. Quite a large percentage of sour hams are thus left
unaccounted for by the thermometer test, and we believe that these
are chiefly the result of contamination carried in on the pumping
needles or in the pumping pickles.</p>
<h5>INFECTION FROM PUMPING NEEDLES.</h5>
<p>In view of the results obtained in the last experiment, in which it
was shown that hams may become infected from the use of ham thermometers,
it seemed not improbable that hams might also become
infected from the pumping needles, which, like the thermometers,
are thrust deep into the bodies of the hams beside the bone. In order
to throw some light upon this point, cultures were taken from the
grease and dirt that accumulate on the shields at the bases of the
pumping needles, as such material must undoubtedly be carried into
the hams at times on the needles. The ham-souring bacillus was
found several times in these cultures, and hence it is fair to infer that
hams may also become infected at times from the pumping needles,
just as they become infected from the thermometers. Bits of contaminated
meat and grease and particles of dirt carried in on the
pumping needles would be forced out into the hams by the pumping
pickle, which passes out through small openings or fenestræ in the
needles, and this probably affords one explanation as to why so many
more body sours occur in the mild-cure hams. In the mild-cure hams,
which are pumped in the shank only, the pumping needle is introduced
near the femorotibial articulation, and the shank is saturated
at the start with a strong brine solution, while the body of the ham is
not. If the ham-souring bacillus were carried into these hams on<span class="pagenum" id="Page_42">[Pg 42]</span>
the pumping needle, the growth of the bacillus in the shank would be
inhibited by the strong brine solution with which the shank is saturated,
but there would be nothing to prevent the bacillus from growing
upward into the body of the ham, which has not been pumped and is
free from pickle. This would also explain the fact that the souring
often starts at the knee joint and extends upward into the body of
the ham. In the case of the regular cure hams, where the ham is
pumped in both body and shank, the entire ham is more or less saturated
at the start with the strong brine of the pumping pickle, which
tends to inhibit the growth of the ham-souring bacillus even if this
bacillus should find its way into these hams on the pumping needles.
It is in the mild-cure or partly pumped hams, where the body of the
ham is left unpumped, that the ham-souring bacillus finds its best
opportunity for development, and the greater proportion of the sours
that occur in the packing house are found in these hams.</p>
<p>As regards the possibility of infection from the pumping pickle
itself, it does not seem probable that this would often occur, for the
pumping and curing pickles are always prepared on an upper floor of
the pickling houses and are delivered to the pickle cellars in closed
pipes, so the chances for the accidental contamination of these solutions
from floating dust or dirt would not be great. Furthermore,
the strong brine of the pumping pickle would completely inhibit the
growth of the ham-souring bacillus, and the bacillus would be incapable
of multiplying, even if it found its way into the pickle. On the
other hand, laboratory experiments show that the bacillus or its
spores may remain alive for a considerable length of time in the pumping
pickle, so the possibility of infection from this source can not be
overlooked.</p>
<h5>INFECTION FROM BILLHOOKS.</h5>
<p>After the hams are cut from the carcasses they are handled entirely
by means of billhooks. In handling the hams the hooks are inserted
beneath the skin of the shank at a point just above the tibio-femoral
articulation. The hooks should be inserted in the connective tissue
beneath the skin and should not penetrate the muscular tissue to
any depth. When the hams lie in the right position, with the butt
or large portion away from and the shank toward the operator, it is
an easy matter to pick them up in the proper manner; but when
they lie at different angles and are being rapidly handled it is almost
impossible to prevent the hook from penetrating the muscular tissues,
and if the hook should penetrate to the bone it might carry in foreign
matter contaminated with the meat-souring bacillus. It is not probable
that many hams become contaminated in this way, as the men
who handle the hams are very skillful in manipulating their hooks;
but the possibility that hams may become contaminated in this
manner should not be entirely overlooked.</p>
<p><span class="pagenum" id="Page_43">[Pg 43]</span></p>
<h3>BIOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS OF THE HAM-SOURING
BACILLUS.</h3>
<h4>CONDITIONS FAVORABLE TO GROWTH.</h4>
<p>The most favorable medium for the growth of the organism was
found to be the modified egg-meat mixture of Rettger, which has
been previously described. In this medium the organism develops
rapidly at a temperature of 20° to 25° C., giving rise to the characteristic
sour-meat odor. Like the bacillus described by Klein, it also
grows readily on pork-agar and pork-bouillon containing glucose,
but differs from Klein’s bacillus in that it will grow, though less luxuriantly,
on ordinary nutrient media—agar, gelatin, and bouillon—without
the addition of glucose.</p>
<p>The optimum temperature for growth is 20° to 25° C. The organism
does not grow at incubator temperature (37.5° C.). At ice-box
temperature (8° to 10° C.) it develops readily, although the growth
is less rapid than at 20° to 25° C. That the organism will develop at
even lower temperatures was shown in the inoculation experiments
with hams, where it developed and multiplied extensively in the
bodies of the hams at the temperature of the pickling cellars, which
are held usually at 34° to 36° F.(1° to 2° C.).</p>
<p>The organism develops best in a neutral or slightly alkaline
medium.</p>
<h4>GROWTH ON DIFFERENT CULTURE MEDIA.</h4>
<p><i>Growth on egg-pork medium.</i>—At a temperature of 20° to 25° C.
the cultures show a slight but distinct sour odor in from two to three
days. This odor, as before stated, closely resembles the odor of a
sour ham. Egg-pork cultures from three to five days old were given
to a trained meat inspector, who knew nothing whatever as to the
contents of the tubes, and he was asked to describe the odor; he
described it as that of a sour ham.</p>
<p>At one week the albumins of the medium are gelatinized or partly
coagulated and the odor is more pronounced. At ten days the
albumins are completely coagulated except at the surface, where
there is no apparent growth; the odor is more putrefactive in nature,
and the reaction of the medium is slightly acid. At three weeks the
coagulated albumin splits up into fragments and appears to undergo
a slow digestion, gas bubbles form in the lower portion of the culture,
and the odor becomes distinctly putrefactive in character. The slow
digestion of the albumin is probably due to a proteolytic enzyme
elaborated by the bacillus.</p>
<p>At the end of a week a dark zone usually appears at the surface of
the coagulated albumin and gradually darkens until it becomes
almost black. This zone is probably due to a pigment elaborated by
the bacillus.</p>
<p><span class="pagenum" id="Page_44">[Pg 44]</span></p>
<p>At ice-box temperature (8° to 10° C.) the same changes and the
same odor were noted, but were somewhat slower in developing.</p>
<p><i>Glucose-pork-agar.</i>—This medium was prepared from pork in the
same manner as beef-agar, and contained 1 per cent of glucose. The
organism grows readily on this medium and may be conveniently
cultivated in deep stab cultures. The medium was always thoroughly
boiled and then rapidly cooled in order to expel the inclosed
air. The growth of the organism was found to vary considerably
with the reaction.</p>
<p>When the reaction was +1.5, deep stab cultures at three days (20°
to 25° C.) showed a well-marked arborescent growth, appearing as
delicate filaments extending outward from the line of stab. The
growth stopped within one-fourth or one-half inch of the surface of
the agar on account of the presence of oxygen in the upper part of
the culture medium. As the growth extended toward the walls of
the test tube the agar became clouded, and there were sometimes gas
bubbles in the depth of the agar, but the gas formation was not
extensive.</p>
<p>When the reaction of the agar is neutral or slightly alkaline, extensive
gas formation occurs and the agar is often much broken up.</p>
<p>The cultures developed a disagreeable, somewhat putrefactive
odor, but did not give the characteristic sour-ham odor obtained from
the egg-pork cultures.</p>
<p>The organism was also grown on anaerobic agar plates by Zinsser’s
method, which is said to give absolutely anaerobic conditions. The
colonies on agar have a cottony or woolly appearance at first, and
spread slowly, with slightly irregular margins.</p>
<p>In glucose-pork-agar to which azolitmin was added the azolitmin
in the lower portion of deep stab cultures was completely decolorized
in five days at room temperature (20° to 25° C).</p>
<p>In glucose-pork-agar containing neutral red the red color in the
lower portion of the tube was changed to yellow with the development
of fluorescence.</p>
<p><i>Neutral gelatin.</i>—Tubes of ordinary neutral gelatin without the
addition of glucose were inoculated and held at ice-box temperature
(8° to 10° C). At five days a delicate white growth appeared along
the line of stab in the lower portion of the tube. At seven days the
growth showed fine radial striæ, presenting an arborescent or tree-like
appearance, and extended halfway from the line of stab to the
walls of the test tube. At two weeks the growth had caused a delicate
clouding of the medium in the lower portion of the tube. At
three weeks the gelatin in the lower portion of the tube had become
liquefied and the growth had settled to the bottom as a white precipitate.</p>
<p><span class="pagenum" id="Page_45">[Pg 45]</span></p>
<p>In gelatin containing glucose, gas bubbles are formed in the depth
of the medium through the splitting up of the glucose, and the
characteristic arborescent growth is obscured.</p>
<p><i>Glucose-pork-bouillon.</i>—This medium was prepared from pork
instead of beef and contained 1 per cent of glucose. The best results
were obtained when the reaction of the medium was neutral or
slightly alkaline.</p>
<p>Culture tubes, which had been previously boiled to expel the contained
air and then inoculated, were held in a Novy jar, in an atmosphere
of hydrogen at a temperature of 20° to 25° C. At three days
the tubes showed well-marked clouding. At one week the growth
appeared as a heavy, white, flocculent, cottony precipitate in the
bottom of the tubes with a slight flocculent precipitate above.
When the culture was removed from the jar and shaken, the heavy,
flocculent precipitate at the bottom of the tube broke up without
much difficulty, giving rise to a heavy uniform clouding with some
small floating masses, which soon settled to the bottom. On shaking
the tube some evolution of gas in the form of very fine bubbles was
noticed.</p>
<p>In Smith fermentation tubes containing neutral glucose-pork-bouillon
the closed arm of the tube shows well-marked clouding with gas
formation at three days at room temperature (20° to 25° C). The
growth has a tufted, cottony appearance, and there are many filaments
and threads. The growth settles to the bottom of the closed
arm as a cottony, white precipitate (see Pl. IV). The organism
splits the glucose vigorously, and at 10 days the tubes show from
40 to 50 per cent of gas. The bouillon in the open arm of the tube
remains unclouded. The maximum gas production at room temperature
is reached in from 10 to 14 days, by which time the growth in the
closed arm has completely settled into the bend of the tube, leaving
the bouillon in the closed arm clear. The gas formula, as determined
by Smith’s method, was H/CO₂= 5/1. The reaction of the bouillon becomes
acid to phenolphthalein.</p>
<p>The organism will grow on ordinary neutral bouillon without the
addition of glucose, and in Smith tubes containing this medium a
small amount of gas was formed, due to the splitting of the muscle
sugar.</p>
<p>The bacillus also grows in a sugar-free broth—that is, a broth free
from muscle sugar—and from cultures grown in this medium a well-marked
indol test was obtained.</p>
<p><i>Litmus-milk.</i>—The organism was grown in litmus-milk in Smith
fermentation tubes at 20° to 25° C. At seven days the litmus in the
lower portion of the closed arm had assumed a brownish-buff color.
At two weeks the litmus in the closed arm had been reduced to a<span class="pagenum" id="Page_46">[Pg 46]</span>
brownish-buff color except at the top of the tube, where a pale,
bluish tinge remained, and the litmus in the open arm showed very
slight reddening as compared with a check tube. At three weeks the
litmus in the closed arm was entirely reduced to a light, brownish-buff
color, and the litmus in the open arm showed a slight but distinct
reddening as compared with the check. The reddening of the
litmus in the open arm was evidently due to the transfusion of acids
formed by the growth of the bacillus in the closed arm. After several
weeks the milk
is slowly peptonized,
probably as a result
of enzyme action.</p>
<h4>MORPHOLOGY.</h4>
<p>The organism is a large bacillus having an average size of 4 to 8 μ
in length by 0.5 to 0.7 μ in thickness, but there are many longer forms
measuring from 10 to 20 μ in length. It develops in long, irregular
chains or filaments, which at times show a slightly spiral form.</p>
<div class="figcenter illowp50" id="fig5" style="max-width: 40em;">
<a href="images/fig5lge.jpg">
<img src="images/fig5.jpg" alt=""/></a>
<div class="caption"><p class="hang"><span class="smcap">Fig. 5.</span>—Ham-souring bacillus
(<i>Bacillus putrefaciens</i>) grown on egg-pork
medium, showing tendency to form chains. Partly developed and
fully developed spores are shown at ends of rods; also free spores.
(Pen-and-ink drawing made with camera lucida from preparation
stained by Gram’s method.× 640.)</p></div>
</div>
<p>The individual organisms show at times a widely open, slightly
spiral form, which was more apparent in hanging-drop preparations made
from bouillon cultures, where the organisms had been comparatively
undisturbed. This appearance was also noted at times in the stained
sections of soured muscular tissue, where the organisms were stained in
place. The organism possesses no motility. It stains with the ordinary
aniline dyes and by Gram’s method.</p>
<h4>SPORE FORMATION.</h4>
<p>The organism develops large, terminal spores, which are at first
oval, but when fully developed are perfectly round and measure
from 1.5 to 2 μ in diameter.</p>
<p>Spores develop rapidly in the egg-pork medium at 20° to 25° C.,
fully developed spores being noted in from five to seven days. At<span class="pagenum" id="Page_47">[Pg 47]</span>
ice-box temperature (8° to 10° C.) partly developed spores were
noted in the egg-pork medium at 10 days and fully developed
spores at 2 weeks.</p>
<p>Occasional spores were noted in old agar and gelatin cultures,
but abundant spore formation was seen only in the egg-pork medium.
No spores were noted in bouillon cultures, even at 10 weeks.</p>
<h4>RESISTANCE TO HEAT AND CHEMICAL AGENTS.</h4>
<p>In its vegetative form the bacillus is killed at 55° C. in 10 minutes.
The spores survive a temperature of 80° C. for 20 minutes, but are
killed at 100° C. in 10 minutes.</p>
<p>When sodium chlorid and potassium nitrate were added to glucose-pork
broth in varying amounts, it was found that 3 per cent of
sodium chlorid or 3 per cent of potassium nitrate was sufficient to
inhibit completely the growth of the bacillus at room temperature
(20° to 25° C.).</p>
<p>While the growth of the bacillus was inhibited by sodium chlorid
and potassium nitrate as just stated, it was found that very much
stronger solutions of the two salts failed to destroy the bacillus.
Thus it was found that the bacillus or its spores retained their vitality
after an exposure of 30 days in a solution containing 23 per cent of
sodium chlorid and 6 per cent of potassium nitrate.</p>
<h4>GAS PRODUCTION.</h4>
<p>The organism splits glucose, but not lactose or saccharose. That
it possesses the power of splitting muscle sugar was shown by the
formation of gas in Smith fermentation tubes containing ordinary
neutral bouillon without the addition of any sugar.</p>
<p>The formation of gas in glucose bouillon varies considerably with
the reaction of the medium. The largest amount of gas was formed
when the broth was neutral or slightly alkaline. When the reaction
of the broth was distinctly acid or distinctly alkaline the amount
of gas was diminished. The gas which is formed in bouillon cultures
consists chiefly of hydrogen and carbon dioxide. In order to collect
a sufficient amount of the gas for analysis, two large fermentation
tubes capable of holding 150 cubic centimeters each were constructed.
These tubes were filled with pork-bouillon and inoculated
with the bacillus. After 20 days at room temperature (20° to 25° C.)
the gas was collected and the carbon dioxide and hydrogen determined,
with the following result:</p>
<table class="standard" summary="">
<tr>
<td class="tdr"></td>
<td class="tdr">Cubic centimeters.</td>
</tr>
<tr>
<td class="tdl">Total amount of gas collected</td>
<td class="tdr">37.7</td>
</tr>
<tr>
<td class="tdl">Carbon dioxide, by absorption with NaOH</td>
<td class="tdr">6.2</td>
</tr>
<tr>
<td class="tdl">Hydrogen, by difference</td>
<td class="tdr">31.5</td>
</tr>
</table>
<p>This analysis gives an approximate gas formula of H/CO<sub>2</sub>= 5/1, which
agrees with the gas formula as determined in the small fermentation
tubes by Smith’s method.</p>
<p><span class="pagenum" id="Page_48">[Pg 48]</span></p>
<p>In hams which had undergone spontaneous souring and in hams
which had been artificially soured by inoculation, hydrogen-sulphid
was often noted when the sour portions of the meat were tested
with lead-acetate paper, but no distinct odor of the gas could be
obtained. Hydrogen sulphid was also noted in egg-pork cultures of
the bacillus.</p>
<h4>ACID PRODUCTION.</h4>
<p>In glucose-bouillon, butyric and lactic acids are formed and the
reaction of the medium becomes distinctly acid. Butyric and lactic
acids were also noted in the egg-pork cultures.</p>
<p>A series of Smith fermentation tubes containing 10 c. c. each of
glucose-pork broth medium was inoculated with the bacillus and
held at room temperature (20° to 25° C.). These cultures were
titrated against [N/40]NaOH, with phenolphthalein as an indicator at
intervals of two days up to nineteen days, and then at two-week
intervals up to sixty-one days. Three of the cultures were titrated
each time so as to give a fair average of the acidity of the cultures,
and an uninoculated check tube was also titrated each time to see
if there was any change in the reaction of the medium. The results
of the titrations are shown in the following table:</p>
<p class="center"><i>Acidity determinations in glucose-pork broth cultures.</i></p>
<table class="standard" summary="">
<tr>
<th class="tdc brdr">Age of culture<br />(days).</th>
<th class="tdc brdr">Culture<br />A.</th>
<th class="tdc brdr">Culture<br />B.</th>
<th class="tdc brdr">Culture<br />C.</th>
<th class="tdc brdr">Average.</th>
<th class="tdc brdr">Medium.</th>
<th class="tdc brdr">Acidity of<br />culture.</th>
</tr>
<tr>
<td class="tdr_br"></td>
<td class="tdr_br"></td>
<td class="tdr_br"></td>
<td class="tdr_br"></td>
<td class="tdr_br"></td>
<td class="tdr_br"></td>
<td class="tdr_br"><i>Per cent.</i></td>
</tr>
<tr>
<td class="tdc_br">2</td>
<td class="tdr_br">0.038</td>
<td class="tdr_br">0.030</td>
<td class="tdr_br">0.040</td>
<td class="tdr_br">0.036</td>
<td class="tdr_br">0.009</td>
<td class="tdr_br">0.027</td>
</tr>
<tr>
<td class="tdc_br">4</td>
<td class="tdr_br">.105</td>
<td class="tdr_br">.100</td>
<td class="tdr_br">.102</td>
<td class="tdr_br">.102</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.093</td>
</tr>
<tr>
<td class="tdc_br">6</td>
<td class="tdr_br">.106</td>
<td class="tdr_br">.110</td>
<td class="tdr_br">.109</td>
<td class="tdr_br">.108</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.099</td>
</tr>
<tr>
<td class="tdc_br">8</td>
<td class="tdr_br">.124</td>
<td class="tdr_br">.115</td>
<td class="tdr_br">.117</td>
<td class="tdr_br">.119</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.110</td>
</tr>
<tr>
<td class="tdc_br">10</td>
<td class="tdr_br">.128</td>
<td class="tdr_br">.130</td>
<td class="tdr_br">.126</td>
<td class="tdr_br">.128</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.119</td>
</tr>
<tr>
<td class="tdc_br">12</td>
<td class="tdr_br">.129</td>
<td class="tdr_br">.120</td>
<td class="tdr_br">.129</td>
<td class="tdr_br">.126</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.117</td>
</tr>
<tr>
<td class="tdc_br">19</td>
<td class="tdr_br">.126</td>
<td class="tdr_br">.125</td>
<td class="tdr_br">.125</td>
<td class="tdr_br">.125</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.116</td>
</tr>
<tr>
<td class="tdc_br">33</td>
<td class="tdr_br">.125</td>
<td class="tdr_br">.123</td>
<td class="tdr_br">.125</td>
<td class="tdr_br">.124</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.115</td>
</tr>
<tr>
<td class="tdc_br">47</td>
<td class="tdr_br">.122</td>
<td class="tdr_br">.120</td>
<td class="tdr_br">.121</td>
<td class="tdr_br">.121</td>
<td class="tdr_br">.009</td>
<td class="tdr_br">.112</td>
</tr>
<tr>
<td class="tdc_brb">61</td>
<td class="tdr_brb">.121</td>
<td class="tdr_brb">.116</td>
<td class="tdr_brb">.119</td>
<td class="tdr_brb">.118</td>
<td class="tdr_brb">.009</td>
<td class="tdr_brb">.109</td>
</tr>
</table>
<p>From the above table it will be seen that the maximum acidity
was reached at ten days, after which there was a gradual reduction
in the acidity, due probably to the formation of ammonia compounds.</p>
<h4>PATHOGENIC PROPERTIES.</h4>
<p>Rabbits, guinea pigs, and white mice were inoculated and fed with
cultures of the bacillus without effect, from which it would appear
that the bacillus possesses no pathogenic or disease-producing
properties.</p>
<h4>NATURE OF THE BACILLUS.</h4>
<p>The bacillus is essentially a saprogenic bacterium with zymogenic
properties. A preliminary study of the chemical changes which take
place in sour hams shows that these changes are of a putrefactive
nature. Hams which had undergone spontaneous souring were compared
with hams which had been artificially soured by inoculation,
and the chemical changes were found to be identical. A chemical
study was also made of the changes taking place in egg-pork cultures
of the bacillus at different stages of growth, and these changes were
found to be of a putrefactive nature and similar in character to the
changes which occur in sour hams. Among the putrefactive products
formed by the growth of the bacillus in the egg-pork medium were
indol, skatol, volatile fatty acids, skatol-carbonic acid, and hydrogen
sulphid.<a id="FNanchor_4" href="#Footnote_4" class="fnanchor">[4]</a></p>
<div class="footnote">
<p><a id="Footnote_4" href="#FNanchor_4" class="label">[4]</a> The tests for the putrefactive products formed by the growth of the bacillus in the egg-pork medium
were made by P. Castleman, of the Biochemic Division, who also determined the percentage composition
of the gas formed by the growth of the bacillus in the glucose-pork-bouillon medium.</p>
</div>
<div class="caption"><span class="smcap center">Bul. 132, Bureau of Animal Industry, U. S. Dept. of Agriculture.</span> <span class="smcap"><a id="Plate_IV"></a>Plate IV.</span></div>
<div class="figcenter illowp80" id="pl4" style="max-width: 50em;">
<img class="w100" src="images/pl4.jpg" alt="" />
<div class="caption"><p class="hang"><span class="smcap">Glucose Bouillon Culture in Smith Fermentation Tube at Four
Days. Culture Grown at Room Temperature (20° to 25° C.).
Growth Confined Entirely to Closed Arm, with Gas Collecting
at Top.</span></p></div>
</div>
<p>A more extended study is now being carried on in the Biochemic
Division of the chemical changes which take place in hams during
the process of souring, together with a further study of the chemical
changes which result from the growth of the bacillus in the egg-pork
medium. The results of this investigation will be given in a later
paper.</p>
<p>The bacillus described in this paper belongs to the class of putrefactive
anaerobes, which are widely distributed in nature in dust, soil,
and excrementitious matters. This group of bacteria contains both
pathogenic and nonpathogenic forms. The former have received
considerable attention, but the latter have never been thoroughly
cleared up. The bacillus isolated from sour hams belongs in the latter
category, being possessed of no pathogenic or disease-producing properties.
It occurs in the dust and dirt of the packing house and finds
its way into the hams in the various manipulations to which the hams
are subjected.</p>
<p>The bacillus described in this paper does not seem to correspond
with any forms heretofore described. It differs from Klei bacillus
(<i>Bacillus fœdans</i>) in the following important particulars:(1) It forms
large terminal spores, whereas Klein’s bacillus formed no spores;(2) it
will grow at a temperature of 34° F., while Klei bacillus did not grow
below 50° F.;(3) it produces an acid reaction in culture media, while
Klei bacillus gave a distinctly alkaline reaction;(4) it will grow on
the ordinary nutrient media—gelatin, agar, and broth—without the
addition of glucose, while Klein’s bacillus did not;(5) it peptonizes
the casein in milk, whereas Klein’s bacillus had no action on milk;
(6) it liquefies gelatin more rapidly, causing complete liquefaction
after three weeks at 8° to 10° C., whereas Klein’s bacillus caused only
partial liquefaction after eight weeks at 20° C.;(7) it can be conveyed</p>
<p><span class="pagenum" id="Page_50">[Pg 50]</span></p>
<p>from turbid broth cultures to new culture material by means of the
platinum loop, whereas Klein’s bacillus could not be thus conveyed.</p>
<p>For the bacillus described in the present paper the following name
is proposed:<i>Bacillus putrefaciens</i>.</p>
<h2>PREVENTION OF HAM SOURING.</h2>
<p>As it has been shown that souring in hams results from the growth
of a bacterium which is introduced into the bodies of the hams in the
various manipulations which the hams undergo, the only way to eliminate
souring in hams, as they are cured in the larger packing establishments,
would be to cure the hams under aseptic or sterile conditions,
which would, of course, be a physical impossibility.</p>
<p>While it will probably be impossible, therefore, to eliminate souring
entirely under the methods of ham curing which are at present employed
in the larger packing establishments, much can undoubtedly
be done toward reducing the percentage of sours. In the matter of
taking ham temperatures, for instance, if the thermometers used were
thoroughly cleaned and disinfected and the surfaces of the hams
seared at the point where the thermometer is introduced, infection
from this source could be entirely prevented; or it might be possible
so to regulate the temperature of the chill rooms that the taking of
ham temperatures could be discontinued.</p>
<p>The elimination of the souring that results from the introduction
of foreign matter on the pumping needles could be effected in two
ways only,(1) by not pumping the hams at all, or (2) by pumping
them under sterile or aseptic conditions. As has been stated before,
some of the smaller packing establishments cure their hams without
pumping, and in these establishments the percentage of sours runs
very low. When hams are cured without pumping, however, the
period of curing has to be materially lengthened in order to give the
curing pickles sufficient time to penetrate thoroughly, and this is
what the larger plants wish to avoid because of the greater space and
greater number of vats which would be necessitated. The object of
pumping in the larger plants, where the number of hams handled
daily runs into the thousands, is to hasten the cure and thus prevent
the accumulation of a great number of hams at one time. It is
doubtful, therefore, whether the larger packing houses could conveniently
discontinue pumping.</p>
<p>To pump the hams under aseptic conditions would necessitate a
technique far too elaborate for routine use in the packing house; in
fact, anything like complete asepsis would be out of the question.
Certain measures might be adopted, however, that would tend to
prevent the possible introduction of ham-souring bacilli in the process
of pumping. It would undoubtedly be safer, for instance, to
boil the pumping pickle before use, and the chances of carrying in<span class="pagenum" id="Page_51">[Pg 51]</span>
contaminated foreign matter on the pumping needles could be lessened
by sterilizing the pumps and needles with boiling water and by frequently
dipping the needles, while in use, in boiling water. If the
hams were sprayed with clean water just prior to pumping, there
would be less likelihood of carrying in foreign matter on the needles.
The danger of introducing contaminated foreign matter on the needles
might be further obviated by searing the surfaces of the hams at
the points where the needles are introduced; but such a procedure
would be hardly practicable in the larger packing houses, where the
great number of hams cured necessitates rapid handling.</p>
<p>While the danger of possible contamination in pumping, through
the introduction of contaminated foreign matter on the pumping
needles, can not well be avoided, this danger is partly counterbalanced
by the inhibitory action of the pumping pickle, which is strikingly
shown in the experiments which have been described. In these
experiments, 100 hams received large doses of the ham-souring bacillus,
half of these hams being subjected to the mild cure and half to the
regular cure, with the following result: In the case of the mild-cure
hams, which were pumped in the shank only, the percentage
of sours was practically 100 per cent, every ham with possibly one
exception becoming sour; whereas in the regular-cure hams, which
were pumped in both body and shank, only 58 per cent of the hams
became sour. In other words, the additional pumping which the
regular-cure hams received served to prevent souring in 42 per cent
of these hams. In these experiments the number of bacteria introduced
into the hams was very great, thousands and even millions of
the bacilli being introduced into each ham, whereas in the routine of
the packing house it is not likely that more than a few of the bacilli
are ever introduced at one time on the thermometers and pumping
needles. In view of these results it is safe to say that in the larger
packing houses, where pumping seems to be necessary, the number
of sours could be reduced fully 50 per cent if all hams were pumped in
the body as well as in the shank.</p>
<p>At present the usual procedure is to pump all hams, both mild and
regular cure, with the same pumping pickle, the mild-cure hams
being pumped in the shank only and the regular-cure hams at two
additional points in the body. The experiments quoted above
show that the additional pumping which the regular-cure hams
receive undoubtedly tends to prevent the development of souring
in these hams, and this result is unquestionably due to the inhibitory
action of the salts contained in the pumping pickle, as it was found
by laboratory experiment that the addition of 3 per cent of sodium
chlorid to culture media is sufficient to inhibit the growth of the
ham-souring bacillus. The pumping pickles consist of strong brine
solutions and always contain considerably more than 3 per cent of<span class="pagenum" id="Page_52">[Pg 52]</span>
sodium chlorid. If, therefore, the pumping of regular-cure hams
were made more thorough than at present, and all of the deeper portions
of the ham were thoroughly saturated with the strong brine
solution, souring could be largely eliminated, if not entirely prevented,
in these hams, as an unfavorable medium or soil would thus be
created in which the ham-souring bacillus could not develop. The
ham-souring bacillus is able to develop within the bodies of the
regular-cure hams because the pumping of these hams is not always
thorough and there are certain areas in the inner or deeper portions
of the hams in which the tissues are not thoroughly saturated with
the pumping pickle.</p>
<p>Under the present methods of curing, the greater proportion of
the sours occur among the partly pumped or mild-cure hams. These
hams are pumped in the shank only, and the growth of the ham-souring
bacillus within the bodies of these hams is not interfered
with until the curing pickle has penetrated from the outside. As
it requires several weeks for the curing pickle to penetrate thoroughly
into the deeper portions of these hams, the bacillus is thus
afforded a considerable interval in which to develop before it is
exposed to the inhibitory action of the pickle. If these hams
could be thoroughly pumped in the body at the beginning of the cure
in the same manner as the regular-cure hams, the chief loss from
ham souring would be eliminated. It would not do, however, to
pump these hams in the body with the same pumping pickle used in
the regular cure, as the meat would be rendered too salty and the
mild flavor of the ham would be lost. There is undoubtedly a demand
for mild-cure hams, otherwise they would not be on the market; and
the question then arises how to pump these hams and still retain a
mild cure. This might be accomplished by pumping these hams
with their own curing pickle, which is usually a milder pickle than
that employed in the regular cure, or an even milder pumping pickle
might be used. If mild-cure hams were pumped in this way, the
percentage of souring in these hams could undoubtedly be greatly
diminished without materially affecting the flavor of the ham.</p>
<p>To recapitulate briefly, the prevention of ham souring is to be
sought in two ways:(1) Through greater care in handling the
hams and the adoption of precautionary measures to prevent the introduction
of the ham-souring bacillus into the bodies of the hams,
and (2) through more thorough pumping of the deeper or inner portions
of the hams, so as to create an unfavorable soil or medium in
which the ham-souring bacillus can not develop even if it should
gain entrance into the bodies of the hams.</p>
<p>From what has been said it will be apparent that ham souring
can probably never be entirely eliminated from the packing house
under the present methods of curing, but the adoption of precaution<span class="pagenum" id="Page_53">[Pg 53]</span>ary
measures in testing and pumping hams, together with a more
thorough pumping of all hams in ways similar to those suggested,
would unquestionably reduce very materially the losses from this
source.</p>
<h2>GENERAL SUMMARY AND CONCLUSIONS.</h2>
<p>1. In this paper it has been shown that ham souring, as encountered
in the wet cure where the hams are entirely submerged in pickling
fluids, is due to the growth of an anaerobic bacillus within the bodies of
the hams. This bacillus (<i>B. putrefaciens</i>) was found in sour hams
obtained from four different packing establishments. It was isolated
and grown in various laboratory media, in one of which, the egg-pork
medium, it gave rise to the characteristic sour-ham odor.
This bacillus was the only organism that could be isolated from sour
hams that was capable of producing the characteristic sour-ham odor
in the egg-pork medium.</p>
<p>2. When injected into the bodies of sound hams, the bacillus
caused these hams to sour in the process of curing. In hams which
had been inoculated with the bacillus and thus artificially soured, the
bacillus was recovered in cultures taken at points far removed,
relatively speaking, from the point of inoculation, indicating that
the bacillus had multiplied and progressed by extension throughout
the bodies of the hams.</p>
<p>3. The bacillus possesses no motility, and its extension throughout
the bodies of the hams is a result of multiplication. In its growth
it follows along the connective-tissue bands between the muscle
bundles, which are composed of comparatively loose tissue and
afford paths of least resistance. When it invades the muscle tissue
proper, it follows along the sarcolemma sheaths between the muscle
fibers. As a result of this growth the muscular tissue becomes softer
and tends to break more easily.</p>
<p>4. The bacillus belongs to the class of putrefactive anaerobes
which are widely distributed in nature in dust, soil, and excrementitious
matters. The bacillus or its spores is present in the dust and
dirt of packing houses and finds its way into the hams in the various
manipulations to which they are subjected.</p>
<p>5. The bacillus or its spores may be introduced into hams on the
thermometers used in testing the hams, on the pumping needles,
and possibly on the billhooks used in handling the hams. It may
also be carried into the hams in the pumping pickle, and may even
find its way into the hams from the curing pickle, although infection
through the latter channel probably does not often occur.</p>
<p>6. The bacillus develops in the deeper portions of the ham because
of the anaerobic conditions there prevailing, and souring is most
often encountered, therefore, in the deeper portions of the ham
near the bone.</p>
<p><span class="pagenum" id="Page_54">[Pg 54]</span></p>
<p>7. A preliminary study of the chemical changes which take place
in the process of souring shows that these changes are of a putrefactive
nature, and ham souring, as ordinarily encountered, is to be
regarded as an incipient putrefaction. Hams which had been
artificially soured by injections of culture were compared with sour
hams obtained from the packing house, and the putrefactive changes
were found to be identical.</p>
<p>8. Hams which have once become sour can never be restored to a
sound condition, because of the chemical changes which result from
the growth of the bacillus. In other words, the tissues of the ham
undergo certain chemical changes in the process of souring, and
when these changes have once taken place the tissues can never be
restored to a sound condition. The repumping of slightly soured
hams with a strong pumping pickle will check further souring, by
inhibiting the growth of the bacillus, but will not restore to a sound
condition those portions of the ham which have become sour.</p>
<p>9. The salts of the pickling fluids have a marked inhibitory action
on the ham-souring bacillus, and sours occur less frequently in regular-cure
hams.</p>
<p>10. In regular-cure hams the growth of the ham-souring bacillus
is restricted and often completely inhibited as a result of the additional
pumping which these hams receive, whereby they are more
or less saturated with pickle at the beginning of the cure.</p>
<p>11. If the pumping of regular-cure hams were more thorough and
all of the deeper portions of the ham were thoroughly saturated
with the pumping pickle, souring could be largely eliminated if not
entirely prevented in the hams, as an unfavorable medium or soil
would thus be created, in which the ham-souring bacillus could not
develop. The reason that souring does develop in regular-cure hams
is because the pumping is not always thorough and there are certain
areas in the deeper portions of these hams which are not saturated
with the pumping pickle.</p>
<p>12. Under the present methods of curing, the partly pumped or
mild-cure hams furnish the greater proportion of the sours, as these
hams are not pumped in the body and the growth of the ham-souring
bacillus within the bodies of these hams is not interfered
with until the curing pickle has penetrated from the outside. As
it requires several weeks for the curing pickle to penetrate thoroughly
into the deeper portions of these hams, the bacillus is thus afforded
a considerable interval in which to develop.</p>
<p>13. The percentage of souring in the mild-cure hams could be
greatly reduced without materially affecting the cure by pumping
these hams with their own curing pickle, which is usually a milder
pickle than that employed in the regular cure; and if the pumping<span class="pagenum" id="Page_55">[Pg 55]</span>
were thorough the number of sours in these hams could be reduced
to a small figure.</p>
<p>14. The only way by which ham souring could be entirely eliminated
from the larger packing establishments under the present methods
of curing would be to handle the hams throughout under aseptic
conditions, and this, for obvious reasons, would be an impossibility.
The losses from ham souring may be materially reduced, however, by
greater care in handling the hams and the adoption of precautionary
measures designed to prevent the introduction of contaminated
foreign matter into the bodies of the hams, together with more
thorough methods of pumping.</p>
<h2>ACKNOWLEDGMENTS.</h2>
<p>In conclusion, the writer desires to express his obligations to Dr.
S. E. Bennett, of the Inspection Division, inspector in charge at
Chicago, for the assignment of trained meat inspectors to assist in
the work, as well as for kind assistance in obtaining data and material
for laboratory study, and to Dr. L. E. Day, of the Pathological
Division, who kindly prepared the sections which are figured and
described in the present article.</p>
<div>*** END OF THE PROJECT GUTENBERG EBOOK 69062 ***</div>
</body>
</html>
|
