INTERNAL DISEASES 391 



The same is true of enteric fever (Plate V., fig. 2), with a 

 few minor differences. It is a disease originally peculiar to 

 man, which does not primarily occur in animals. 



On the other hand, most experimental animals are suscept- 

 ible to this disease. But the characteristic typhoid symptoms 

 are absent, and at the autopsy, except in the case of apes, 1 

 the typhoid ulceration is not found in the small intestine. The 

 animals simply die of typhoid septicaemia (Marx). 



Fowl typhoid or fowl cholera is a disease which is never 

 communicated to man, but at certain times numbers of fowls 

 and other birds die of it. Infection with the short non-motile 

 bacillus produces profuse diarrhoea, rapidly increasing weakness 

 and cramps. 



In contrast to cholera and enteric fever plague does not 

 attack man only, but also primarily affects other warm-blooded 

 animals, including apes, rats and mice. Birds, horses, cows, 

 sheep and goats are quite insusceptible to the bacillus dis- 

 covered in 1894 by Kitasato and Yersin. These animals are, 

 however, susceptible to the poisons contained in the bodies of 

 the bacilli ; recently it has been discovered that fleas and flies 

 may become fatally infected, apparently from rats. If the 

 skin of a guinea-pig is artificially infected with the plague 

 bacillus, pustules containing the organism form on the skin 

 and the animal dies ; haemorrhagic cedema of the subcutaneous 

 tissue takes place, and the lymphatic glands are considerably 

 enlarged (Marx). 



The bacillus of tuberculosis, first discovered and investi- 

 gated in pure culture by R. Koch, is not only pathogenic for 

 man, but also for guinea-pigs, rabbits, rats and dogs. Accord- 

 ing to M. Schmidt, it is the most frequent cause of death 

 among the apes and large felidae in the Zoological Gardens, 

 whereas bears and the smaller beasts of prey are less frequently 

 attacked. The only distinction between man and these 

 animals is that in the latter tubercles are not formed in the 

 viscera, though they are loaded with tubercle bacilli and undergo 

 finally the same destructive process. 



Fowl tubercle and bovine tubercle are somewhat specific, 

 although there is no doubt that all these kinds arise from a 

 1 Grunbaum, B. M. Journal, 1905. 



