466 POPULAR SCIENCE MONTHLY. 



Of the experiments which I have carried out during the last two years 

 along with Professor Schiitz of the Veterinary College in Berlin I will 

 tell you briefly some of the most important. 



A number of young cattle which had stood the tuberculin test, and 

 might therefore be regarded as free from tuberculosis, were infected in 

 various ways with tubercle bacilli taken from cases of human tuber- 

 culosis; some of them got the tuberculous sputum of consumptive 

 patients direct. In some cases the tubercle bacillus or the sputum was 

 injected under the skin, in others into the peritoneal cavity, in others 

 into the jugular vein. Six animals were fed with tuberculous sputum 

 almost daily for seven or eight months; four repeatedly inhaled great 

 quantities of bacilli, which were distributed in water and scattered 

 with it in the form of spray. None of these cattle (there were 19 of 

 them) showed any sjmptoms of disease and they gained considerably 

 in weight. From six to eight months after the beginning of the ex- 

 periments they were killed. In their internal organs not a trace of 

 tuberculosis was found. Only at the places where the injections had 

 been made small suppurative foci. had formed, in which few tubercle 

 bacilli could be found. This is exactly what is found when dead 

 tubercle bacilli are injected under the skin of animals liable to con- 

 tagion. So the animals we experimented on were affected by the liv- 

 ing bacilli of human tuberculosis exactly as they would have been by 

 dead ones ; they were absolutely insusceptible to them. 



The result was utterly different, however, when the same experiment 

 was made on cattle free from tuberculosis with tubercle bacilli that 

 came from the lungs of an animal suffering from bovine tuberculosis. 

 After an incubation-period of about a week the severest tuberculous dis- 

 orders of the internal organs broke out in all the infected ani- 

 mals. It was all one whether the infecting matter had been injected 

 only under the skin or into the peritoneal cavity or the vascular system. 

 High fever set in and the animals became weak and lean ; some of them 

 died after from one and a half to two months; others were killed in 

 a miserably sick condition after three months. After death extensive 

 tuberculous infiltrations were found at the place where the injections 

 had been made and in the neighboring lymphatic glands, and also far- 

 advanced alterations of the internal organs, especially of the lungs and 

 the spleen. In the cases in which the injection had been made into 

 the peritoneal cavity the tuberculous growths which are so character- 

 istic of bovine tuberculosis were found on the omentum and peri- 

 toneum. In short, the cattle proved just as susceptible to infection by 

 the bacillus of bovine tuberculosis as they have proved insusceptible 

 to infection by the bacillus of human tuberculosis. I wish only to 

 add that preparations of the organs of the cattle which were artificially 

 infected with bovine tuberculosis in these experiments are exhibited 

 in the museum of pathology and bacteriology. 



