2. A small, nonmotile, gram-negative bacillus, about the size of Bacillus coli and usually in pairs.
3. A large micrococcus.
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.
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 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.
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.
INOCULATION EXPERIMENTS WITH HAMS.
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.
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.
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.