256 CLINICAL BACTERIOLOGY. 



Spontaneous and Experimental Tuberculosis in Ani- 

 mals. Spontaneous tuberculosis occurs in animals, with 

 frequency only among cattle and in monkeys living in 

 captivity, although there is scarcely a domestic animal that 

 is immune to tuberculosis. Among laboratory-animals the 

 guinea-pig is the most susceptible, a few tubercle-bacilli 

 sufficing to induce infection in them. Next in suscepti- 

 bility is the rabbit, and then the field-mouse. Less sus- 

 ceptible, though by no means immune, are white mice and 

 dogs. Young animals exhibit a much greater predisposi- 

 tion to tuberculosis than old animals. Typical tubercu- 

 lous disease is induced experimentally in animals (guinea- 

 pigs, rabbits, field-mice) by means of subcutaneous injec- 

 tion, by inoculation of the anterior chamber of the eye, by 

 intrapleural, intraperitoneal, and intravenous injection, or 

 by inhalation of moist tubercle-bacilli in the form of dust. 

 The last remaining portal of entry for tubercle-bacilli into 

 the organism, the gastro-intestinal tract, also was utilized suc- 

 cessfully by Koch in experiments on animals. Susceptible 

 animals that are given tubercle-bacilli in considerable num- 

 ber with their food die of intestinal tuberculosis. The re- 

 sulting tuberculous process is, apart from the results of 

 intravenous injection, at first always local, restricted to 

 the site of infection ; it extends, however, steadily, but 

 slowly, by way of the lymph-paths. The bacilli quickly 

 gain entrance into the lymph-glands nearest the portal of 

 infection. As early as three days after inoculation of 

 tuberculous material into the anterior chamber of the eye 

 Baumgarten found that the bacilli had advanced as far as 

 the auricular lymph-glands. When the bacilli are injected 

 into a vein, general miliary tuberculosis takes place at once. 



Of great assistance in the comprehension of some tuber- 

 culous local processes in human beings are the observations 

 of. Schuller, who inoculated tuberculous material at some 

 indifferent portion of the body of the animal and then in- 

 flicted traumatism in the neighborhood of the knee-joint, 

 and found that the infection localized itself at this point. 



The chronic cold abscesses, which upon bacteriologic ex- 

 amination are found free from pyogenic microbes, are cer- 

 tainly to be attributed to tubercle-bacilli. Dead tubercle- 

 bacilli, destroyed by live steam or by other means, exhibit 

 pyogenic activity experimentally. They are positively 

 chemotactic : they attract leukocytes. The pyogenic sub- 



