PA THOLOGY OF HYDROPHOBIA. 469 



from the nerves of the limb which was infected. Further, 

 rabies can often be produced from such a case by subdural 

 infection with the part of the spinal cord into which 

 these nerves pass, while the other parts of the animal's 

 nervous system do not give rise to the disease. This 

 explains how the initial symptoms of the disease (pains 

 along nerves, paralyses, etc.) so often appear in the infected 

 part of the body, and it probably also explains the fact that 

 bites in such richly nervous parts as the face and head are 

 much more likely to be followed by hydrophobia than bites 

 in other parts of the body. Again, injection into a peri- 

 pheral nerve, such as the sciatic, is almost as certain a 

 method of infection as injection into the subdural space, 

 and gives rise to the same type of symptoms as injection 

 into the corresponding limb. Intravenous injection of the 

 virus, on the other hand, differs from the other modes of 

 infection in that it more frequently gives rise to paralytic 

 rabies. This fact Pasteur explained by supposing that the 

 whole of the nervous system in such a case becomes 

 simultaneously affected. The virus seems to have an 

 elective affinity for the salivary glands, as well as for the 

 nervous system. Roux and Nocard found that the saliva 

 of the dog became virulent three days before the first 

 appearance of symptoms of the disease. 



As we have said, of the causa causans in hydrophobia we 

 are ignorant. There is no evidence that the granules ob- 

 served in the nervous system of animals dead of this disease 

 are bacteria, and no organisms which certainly reproduce 

 rabies have been cultivated from any part of the body of 

 such animals. We are likewise ignorant of the nature of 

 the hydrophobic virus. Whether it is a ferment, as the 

 occurrence of such a marked period of incubation might 

 indicate, we do not know. It must be of a fairly stable 

 nature, as the nervous system containing it is virulent till 

 destroyed by putrefaction. Further, Jobert kept a rabbit's 

 nervous system for a year at - 10 to - 20 C, and found 

 that its virulence remained unimpaired. Whatever its nature 

 may be, the potency of the virus seems to vary. Such 



