On Babies. 



63 



The infeotivity of the blood of rabid animals has been a moot 

 question, some accounts having asserted infection to have been, pro- 

 duced by inoculation with it, the experiments having, of course, been 

 made by subcutaneous inoculation. 



I have taken blood from the heart of a rabbit recently dead of 

 rabies, defibrinated it by whipping with a sterilised glass rod, and 

 injected portions of 0*1 c.c. subdurally in rabbits, but have not 

 succeeded in producing infection, the animals as long as observed 

 being unaffected in any way. 



It seems probable that, as in other analogous cases, this fluid is but 

 exceptionally infective, or only so in large quantities, as it is not 

 the primary seat of the virus, which we now know to be principally 

 in the tissues of the central nervous system. 



The value of these methods of intracranial inoculation with rabbits, 

 from the greatly curtailed incubation period and practically certain 

 resulting infection, for the purpose of determining whether a suspected 

 case is one of true rabies or not, is obvious. 



In one instance a dog was destroyed at Caterham in a state, 

 apparently, of furious rabies, after having bitten several persons and 

 other dogs ; as it was very desirable to ascertain positively the nature 

 of the case, I inoculated from a portion of its medulla a rabbit, which 

 after sixteen days developed symptoms of infection, and died shortly 

 afterwards of paralytic rabies. 



In another instance I received a portion of the spinal cord of a dog 

 that had bitten several persons at Grantham, but which, as was stated, 

 showed no symptoms of rabies ; from the cord I inoculated a rabbit 

 by trephining, and after nineteen days symptoms of infection appeared, 

 the animal dying in the usual manner, leaving no doubt as to the dog 

 having been rabid. 



The duration of the incubation period, too, being proportionate to 

 the activity of the virus, which varies from different sources, may 

 in case of death from hydrophobia, afford a means of determining the 

 source whether, e.g., infection arose from the bite of a rabid street 

 dog, or was caused by inoculation with rabbit virus. 



This must, however, be received with some reservation, the incuba- 

 tion period resulting from inoculation with the virus of street rabies in 

 some cases, though very exceptionally, being even shorter than that 

 of the Pasteurian or constant rabbit virus, as shown in two of my 

 experiments (supra, p. 58) where in a dog and rabbit inoculated sub- 

 durally from the cord of a street dog, this period was respectively 

 seven and five days, and in another rabbit similarly inoculated from 

 the last-mentioned dog, it was only four days. 



