THE VIRUS OF HYDROPHOBIA 513 



entrance by the infected wound, it early manifests its affinity for 

 the nervous tissues. It reaches the central nervous system 

 chiefly by spreading up the peripheral nerves. This can be 

 shown by inoculating an animal jsubcutaneously in one of its 

 limbs, with virulent material, ^tf now the animal be killed 

 before symptoms have manifested themselves, rabies can be 

 produced by subdural inoculation from the r^erves 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, paralysis, 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 peripheral 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. In certain animals 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. 



The Virus of Hydrophobia. While a source of infection 

 undoubtedly occurs in all cases of hydrophobia, and can usually 

 be traced, all attempts to determine the actual morbific cause 

 have been unsatisfactory. In this connection various organisms 

 have been described as being associated with the disease. 



Thus Memmo has isolated an organism which resembles a yeast, but 

 which he places amongst the blastomycetes, and with which he states 

 he has produced both types of rabies in rabbits and dogs. Bruschettini 

 also, by using media containing brain substance, has grown a bacillus 

 having some resemblances to the members of the diphtheria group, and 

 with which he claims to have produced paralytic rabies in rabbits. In 

 the case of the work of neither of these observers has there been con- 

 firmation from independent sources, and in neither case is there evidence 

 of the crucial test having been applied, namely, that of immunising 

 animals against the ordinary hydrophobia virus by means of pure 

 cultures of the alleged causal organism. With regard to other possible 

 33 



