392 THE HUMAN SPECIES 



common stem (Marx), and may be grown on suitable media at 

 37~38 C., although the optimum temperature is4O-4i C. 



Cultures are somewhat slimy in character and cannot be 

 inoculated into guinea-pigs. As yet it has not been found 

 possible to convert fowl tubercle into mammalian tubercle or 

 human into bovine tubercle by experimental methods. Koch 

 indeed considers that the transmission of human tubercle to 

 cattle has been shown to be impossible. 1 Cattle may become 

 immune to infection with human tubercle without any apparent 

 illness. 



The " Perlsucht " of cattle arises from another bacillus, 

 very closely related to the human, and is not, as Behring states, 

 identical with the latter.- 



A pathogenic bacillus closely related to that of tuberculosis 

 is the bacillus of leprosy (Plate V., fig. 3), although numerous 

 researches and experiments have shown marked differences 

 between the two diseases. It is a remarkable fact that the 

 bacillus of leprosy cannot be cultivated, and a still more 

 remarkable one that it occurs almost exclusively in human 

 epithelial cells. The main point of difference consists in the 

 fact that leprosy is an exclusively human ailment and has 

 never been communicated to animals. 



The bacillus of diphtheria discovered by Klebs in 1883, and 

 Loeffler in 1884, in addition to man attacks both cats and 

 horses, and, according to Schmidt, apes may also be infected, 

 though spontaneous infection in these animals is rare. On the 

 other hand, all mammals, with the exception of rats and mice, 

 and also fowls and pigeons, may be artificially infected. When 

 guinea-pigs are infected the lymphatic glands are enlarged, the 

 animals become weak and cyanosed and die of suffocation. 

 The post-mortem appearances are similar to those seen in man, 

 viz,, haemorrhages, oedema, serous effusion into the pleura, 

 pericardium and peritoneal cavity, and considerable engorge - 



1 The possibility of such an infection was proved at the Imperial Society of 

 Hygiene in 1905. 



2 Dr. Paul Bartels -has brought forward interesting evidence before the 

 German Anthropological Society at Gorlitz (1906), showing that tuberculosis has 

 been one of the deadliest enemies of man from the earliest times. In a neo- 

 lithic grave, together with tools, he found human vertebras showing clear signs 

 of tuberculous disease which had healed, leaving an " angular curvature ". 



