The difference between human and bovine tuberculosis appeared not less strikingly in a similar experiment with asses, sheep, and goats, into whose vas cular systems the two kinds of tubercle bacilli were injected.
These experiments are not the only ones that have led to this result. If one studies the older literature of the subject, and collates the reports of the numerous experiments that were made in former times by Chauveau, Gfinther and Harms, Bollinger, and others, who fed calves, swine, and goats with tuber culous material, one finds that the ani mals that were fed with the milk and pieces of the lungs of tuberculous cattle always fell ill of tuberculosis, whereas those that received human material with their food did not. Comparative investigations regarding human and bo vine tuberculosis have been made very recently in North America by Smith, Dinwiddie, and Frothinghain, and their result agreed with the above.
Considering all these facts, it may be maintained that human tuberculosis differs from bovine, and cannot be trans mitted to cattle.
But, now, how is it with the suscepti bility of man to bovine tuberculosis? It is impossible to give this question a direct answer, because the experimental investigation of it with human beings is out of the question. Indirectly, how ever, one can try to approach it. It is well known that the milk and butter consumed in great cities very often con tain large quantities of the bacilli of bovine tuberculosis in a living condi tion, as the numerous infection experi ments with such dairy products on animals have proved. Most of the in habitants of such cities daily consume such living and perfectly virulent bacilli of bovine tuberculosis, and unintention ally carry out the experiment which one is not at liberty to make. If the bacilli of bovine tuberculosis were able to in fect human beings, many cases of tuber culosis caused by the consumption of alimenta containing tubercle bacilli could not but occur among the inhab itants of great cities, especially the chil dren. Most medical men believe that this is actually the ease.
In reality, however, it is not so. That a case of tuberculosis has been caused by alimenta can be assumed with cer tainty only when the intestine suffers first—that is, when a so-called primary tuberculosis of the intestines is found.
But such cases are extremely rare. Among 933 eases of tuberculosis in chil dren at the Emperor and Empress Fred erick's Hospital for Children, Baginsky never found tuberculosis of the intestine without simultaneous disease of the lungs and the bronchial glands. Among 3104 necropsies of tuberculous children, Biedert observed only 16 cases of pri mary tuberculosis of the intestine. It is by no means certain that these few cases were due to infection by bovine tuberculosis. It is just as likely that they were caused by the widely-propa gated bacilli of human tuberculosis, which may have got into the digestive canal in some way or other. Hitherto nobody could decide with certainty in such a case whether the tuberculosis of the intestine was of human or of animal origin. Now one can diagnose them. All that is necessary is to cultivate in pure culture the tubercle bacilli found in the tuberculous material, and to as certain whether they belong to bovine tuberculosis by inoculating cattle with them. For this purpose, subcutaneous injection, which yields quite specially characteristic and convincing results, is recommended.
Though the important question of whether man is susceptible to bovine tuberculosis at all is not yet absolutely decided, and will not admit of absolute decision to-day or to-morrow, one is nevertheless already at liberty to say that, if such a susceptibility really exists, the infection of human beings is but a very rare occurrence. It is esti mated that the extent of the infection by the milk and flesh of tuberculous cattle, and the butter made of their milk, as hardly greater than that of hereditary transmission, and therefore it is not deemed advisable to take any measures against it.
So the only main source of the infec tion of tuberculosis is the sputum of consumptive patients, and the measures for the combating of tuberculosis must aim at the prevention of the dangers arising from its diffusion. Robert Koch (Brit. Jour.. July 27, 1901).