470 ANNUAL REPORT OF THE Off. Doc. 



jection, tuberculous material from man. (Acute phthisis or caseous 

 pneumouia). These four animals were killed at different times up to 

 fiftj-nine davs, and at the autopsy showed very important lesions, 

 manifestly the result of the experimental infection. 



In two of the three calves infected by ingestion the lesions were 

 confluent in the intestiii^^, the mesenteric glands, and on the periton- 

 eum. In the third calf, on the contrary, while there were slight le- 

 sions of the abdominal organs, there existed very important ones in 

 the glands related to the first part of the digestive tract, namely, 

 the retropharyngeal and oesophageal glands. 



Some will, no doubt, raise the objection to these experiments, that 

 datiog back to a period so far in the past, when tuberculin was not 

 known, it was impossible to be sure that the calves used in the ex- 

 periment were free from tuberculosis. Chauveau had foreseen this 

 objection. He had chosen young calves for his experiments because 

 tuberculosis in calves is extremely rare. He procured these calves 

 in a district where tuberculosis of cows was unknown; and finally, 

 in each experiment he preserved as controls an equal number of 

 calves of the same age a«d origin, which were killed at the same 

 time as the others, and were found to be absolutelv free from tuber- 

 culosis. 



Old as they may be, these experiments of Chauveau have on that 

 account none the less value as positive facts against which negative 

 experiments cannot prevail, however numerous they may be. Fur- 

 thermore, several members of this Congress are announced to com- 

 municale analogous facts with the proofs. 



These facts prove that although it may be difficult to communicate 

 human tuberculosis to cattle, it nevertheless succeeds at times. 

 How can Ave explain these different results apparently contradic- 

 tory? It is difficult to do this with certainty, for we cannot pretend 

 that we are able to reproduce exactly in our experiments all the con- 

 ditions of natural infection. It is, however, possible to give a plausi- 

 ble explanation. It is a well known general law that the gradual 

 adaptation of any parasite to a medium, inert or living, in which it 

 can succeed in developing, confers on it the aptitude to develop more 

 easily in media like the first. This is true for the bacillus of tuber- 

 culosis as for all other microbes. We know how difficult it is to ob- 

 tain the first growth of the bacillus of Koch even on the most favora- 

 ble culture medium. The first culture is alwavs thin and scaotv, 

 but when once accustomed to our culture medium, it grows after- 

 wards quite quickly and abundantly. What is true of inert media 

 is still more true, a fortiori, of living media. Every one knows that 

 the bacillus of '^rougct du pore" develops with difficulty at first in 

 the organism of the rabbit. In order to kill one rabbit with cer- 

 tainty it is necessary to inoculate three of four animals, and death 



