EXPERIMENTAL INOCULATION. 223 



minute and grey, or larger and of a yellowish tint. If death 

 has been long delayed, calcification may have occurred in 

 some of the nodules. Tubercle nodules, though rather 

 less numerous, are also present in the liver and in the lungs, 

 the nodules in the latter organs being usually of smaller 

 size, though sometimes extremely numerous. The extent 

 of the general tuberculosis varies in different cases, some- 

 times chronic glandular changes being the outstanding 

 feature. 



Intraperitoneal injection of pure cultures produces a 

 local lesion in the form of an extensive tubercular infiltra- 

 tion and thickening of the omentum, sometimes attended 

 with acute tubercles all over the peritoneum. There is a 

 caseous enlargement of the retro -peritoneal and other 

 lymphatic glands, and later there may be a general tuber- 

 culosis. Intravenous injection produces a typical acute 

 tuberculosis, the nodules being usually more numerous and 

 of smaller size, while death follows more rapidly, generally 

 within three weeks, the larger the numbers of bacilli injected. 

 Guinea-pigs, when fed with tubercle bacilli, or with sputum 

 or portions of tissue containing them, readily contract an 

 intestinal form of tuberculosis, lesions being present in the 

 lymphoid tissue of the intestines, in the mesenteric glands, 

 and later in the internal organs. 



Rabbits are less susceptible than guinea-pigs, and in them 

 the effects of subcutaneous inoculation are somewhat 

 variable, as sometimes the lesions remain local, sometimes 

 a general tuberculosis is set up. Otherwise the reactions 

 are much of the same nature. Dogs are much more highly 

 resistent, but tuberculosis can be produced in them by 

 intraperitoneal injections of pure cultures (Koch), or by 

 intravenous injection (Maffucci). In the latter case there 

 results an extensive eruption of minute miliary tubercles. 



Tuberculosis can also be easily produced in susceptible 

 animals by making them inhale the bacilli. Koch, for this 

 purpose, used pure cultures which were mixed with dis- 

 tilled water, and then distributed in the air by means of a 

 spray. Rabbits, guinea-pigs, and mice were exposed by 



