INTERNAL DISEASES 393 



ment of the internal organs. The proper fowl diphtheria 

 differs from the human variety, and is caused by a special 

 bacillus of a different type. 



The bacillus which gives rise to lockjaw or tetanus prim- 

 arily attacks many mammals ; it is, however, specially dangerous 

 to all kinds of horses ; it may be conveyed by infection to 

 other mammals, especially guinea-pigs and rodents, whereas 

 fowls are nearly insusceptible to the tetanus poison. Cases 

 occurring spontaneously, or due to artificial infection, exhibit 

 the same symptoms, viz., muscular contractions, gradually in- 

 creasing in severity, till life eventually becomes extinct owing 

 to paralysis of the respiratory muscles ; these phenomena also 

 occur in man. 



The causal organism of influenza was long sought for and 

 eventually discovered by Pfeiffer in 1893 (Plate; V., fig. 4). Man 

 alone is attacked during any epidemic, and it was long thought 

 that animals could not be artificially infected. Pfeiffer, how- 

 ever, has succeeded in conveying the disease to apes. The 

 influenza ("Pink-eye") in horses is not identical with the 

 human disease, and is caused by a different organism. 



Whooping cough, not only in its symptoms, but also in its 

 almost absolute limitation to man, resembles influenza most 

 nearly. It has not been determined whether the short thick 

 bacillus described by Jochmann and Krause is the actual 

 cause of this disease. 



As long ago as 1873 tne spirillum discovered by Obermeier 

 was recognised as the cause of relapsing fever (Plate V., fig. 5). 

 Tictin discovered that the transmission of the spirillum, and 

 with it of the disease, from man to man took place by means 

 of the bed bug, and that apes could be infected by crushed bugs. 



As far as is now known spontaneous cases occur only in 

 man ; even fowls are not attacked, though whole nests of bugs 

 are often found in fowl-yards ; we must conclude from this 

 that relapsing fever is peculiar to man, and that when bugs 

 attack and infect fowls, they are immune to the spirillum. 

 R. Koch reported on his return from German East Africa that 

 African relapsing fever was only a variety of the European, 

 and was caused by a spirillum of rather larger size. He 

 charged a kind of tick (ornithodorus monbata) with being the 



