HYDROPHOBIA. 511 



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 hmb. 

 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. 



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 associ- 

 ated 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 diph- 

 theria group, and with which he claims to have produced paralytic 

 rabies in rabbits. In the case of the work of neither of these observers 

 lias there been confirmation 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 hydrophobic virus by 

 means of pure cultures of the alleged causal organism. With regard to 

 other possible causal agents, Grigorjew thinks such may be found in 

 a protozoon which he has constantly observed after inoculation in the 

 cornea. There is no doubt that between rabies and the bacterial dis- 

 eases we have studied there are at every point analogies, the most strik-. 

 ing being the protective inoculation methods which constitute the great 

 work of Pasteur, and everything points to a micro-organism being the 

 cause. Judging from our knowledge of similar diseases we would 

 strongly suspect that it is actually present in a living condition in the 

 central nervous system, the saliva, etc., which yield what we have called 

 the hydrophobic virus, for by no mere toxin could the disease be trans- 

 mitted through a series of animals, as we shall presently see can be done. 

 The resistance of the virus to external agents varies. Thus a nervous 

 system containing it is virulent till destroyed by putrefaction ; it can re- 

 sist the prolonged application of a temperature of from — 10° to — 20° 

 C, but, on the other hand, it is rendered non-virulent by one hour's 



