EXPERIMENTAL INOCULATION 247 



the animals generally used for the purpose, the guinea-pig is 

 most susceptible. 



When a guinea-pig is inoculated subcutaneously with tubercle 

 bacilli from a culture, or with material containing them, such as 

 phthisical sputum, a local swelling gradually forms which is 

 usually well marked about the tenth day. This swelling becomes 

 softened and caseous, and may break down, leading to the 

 formation of an irregularly ulcerated area with caseous lining. 

 The lymphatic glands in relation to the parts can generally be 

 found to be enlarged and of somewhat firm consistence, about 

 the end of the second or third week. Later, in them also caseous 

 change occurs, and a similar condition may spread to other 

 groups of glands in turn, passing also to those on the other side 

 of the body. During the occurrence of these changes, the animal 

 loses weight, gradually becomes cachectic, and ultimately dies, 

 sometimes within six weeks, sometimes not for two or three 

 months. Post mortem, in addition to the local and glandular 

 changes, an acute tuberculosis is usually present, the spleen 

 being specially affected. This organ is swollen, and is studded 

 throughout by numerous tubercle nodules, which may be 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 occasionally in 

 large numbers. The extent of the general infection varies; 

 sometimes the chronic glandular changes constitute the out- 

 standing feature. 



Intraperitoneal injection of pure cultures produces a local lesion in the 

 form of an extensive tubercular infiltration and thickening of the 

 omentum, sometimes attended with acute tubercles all over the 

 peritoneum, There is a caseous enlargement of the retroperitoneal and 

 other lymphatic glands, and later there may be a general tuberculosis. 

 Intravenous injection produces a typical acute tuberculosis, the nodules 

 being usually more numerous and of smaller size, while death follows 

 more rapidly, 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 very variable ; 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 

 resistant, but tuberculosis can be produced in them by intraperitoneal 

 injection of pure cultures (Koch), or by intravenous injection (Maffucci). 

 In the latter case there results an extensive eruption of minute miliary 



