44 TUBERCULOSIS 



cent.) the infection has been found to be a mixed one, both varieties 

 being present. This, however, does not tell the whole story. 



In pulmonary tuberculosis in adults the bovine variety is rare (4 

 cases out of 732) . In tuberculosis of the bones and joints, at all ages, the 

 bovine variety occurs more frequently (5 cases out of 98). In menin- 

 geal tuberculosis at all ages the frequency is still greater (3 cases out 

 of 32). In general tuberculosis at all ages there is a further increase 

 (33 cases out of 172). In tuberculosis of the glands of the neck, the 

 proportion is still higher (45 cases out of 157). In tuberculosis of 

 the abdominal organs the presence of the bovine variety reaches its 

 highest point (30 cases out of 99). 



When we study the proportion of the two varieties in adults and 

 in children, we get more practical information. In children 23.8 per 

 cent, of generalized tuberculosis, 40 per cent, of tuberculosis of the 

 cervical glands and 49 per cent, of tuberculosis of the abdominal 

 organs are due to infection with the bovine variety. It is quite natural 

 that the greater number of cases of bovine tuberculosis should be 

 found among children. These figures demonstrate that the character 

 of the milk cannot be neglected with safety in the crusade against 

 tuberculosis. At the same time, they show that the chief source of 

 infection in man is the human variety and that as a rule tuberculosis is 

 transferred from man to man. 



The Avian Type. The barnyard fowl is frequently tuberculous. 

 Much of the poultry that comes to market, when properly inspected, 

 shows enlarged livers filled with yellowish tuberculous nodules. This 

 variety of the tubercle bacillus can be distinguished morphologically 

 and culturally from other forms. Chickens are easily infected by 

 feeding, developing intestinal and hepatic tuberculosis and loss of 

 weight. Intravenous injection, even of a minute quantity, leads to 

 rapid emaciation and death may result before macroscopical changes 

 are in evidence. In less rapid cases the liver shows the characteristic 

 enlargement and nodules. Intraperitoneal and intramuscular inocula- 

 tions are slower, but in time develop the disease. Ducks and pigeons 

 may be infected, but in nature the disease is much less frequent in 

 these than in chickens. 



The testimony concerning the susceptibility of the guinea-pig to 

 this variety of the tubercle bacillus is conflicting. Evidently it is less 



