Natural Infection. 469 



"bility of infection of the uninjured mucous membrane cannot 

 be disputed in consideration of the recorded positive results 

 of experiments. 



After the bite of rabid animals the disease follows only 

 in a portion of the cases, hardly more than half. As already 

 mentioned there is a possibility that the contagion will not 

 reach the wound or may be carried away by bleeding ; besides, the 

 virus may be removed or destroyed by means of immediate 

 disinfection. Probably, in many cases, the rabies virus is de- 

 stroyed without causing the disease after having entered the 

 body. In favor of this possibility- is the experience that bites 

 from various animals are not of equal danger in the various 

 parts of the body, and also that artificially infected susceptible 

 animals do not always contract the disease, while a few cases 

 ultimately recover. The animal organism is undoubtedly capa- 

 ble under certain circumstances of rendering the contagion in- 

 effective, when the virus is present in small amount or is at- 

 tenuated, and this power is decidedly increased by measures 

 of immunization. Thus only can it be explained why barely 

 30-40% of dogs bitten by rabid animals eventually develop the 

 disease. On the other hand it is possible that latent virus 

 in the brain and spinal cord is stimulated to rapid increase 

 by external influences, such as physical exertion, cold, etc., 

 whereupon the disease which until this time had been latent, 

 may develop within a short time (Marie, Eemlinger). 



According to a compilation of Friedberger & Frohner, animals bitten by rabid 

 dogs afterwards contract the disease as follows : According to Hertwig, 5% ; 

 according to Haubner 40%; according to the calculations of the Lyon school 20%; 

 according to those of the Alfort school 33%, according to KoU, in Austria, in the 

 years 1877-1887, 40% of bitten horses, 50% of cattle and sheep, 36% of hogs, and 

 20% of goats contracted the disease. As a general average 30% may be adopted, 

 although for cattle and sheep 50-60% will be reached. 



Eegarding susceptibility to rabies there exists no con- 

 siderable difference among the mammals. While the disease 

 has been observed very frequently in certain species of animals, 

 this may be explained satisfactorily by their mode of living, 

 their manner of commingling, and by a temperament favorable 

 to mutual infection. Therefore, the disease is observed most 

 frequently in vagrant, vicious dogs, then in cats and wild 

 carnivorous animals, and it is transferred to animals of this 

 class by means of bites, while herbivorous animals infect each 

 other only exceptionally. 



The breed or the sex of the animal as well as climatic 

 factors are without influence on the susceptibility, and age is 

 a factor insofar as in young animals the outbreak of the disease 

 will follow after a shorter period of incubation. According 

 to Eemlinger 1 to 2 months old puppies are very susceptible 

 to rabies and the virus in their bodies is very virulent since 

 it produces typical rabies by subdural and intraocular injec- 

 tion in 9 to 13 days. The more frequent appearance of the 



