Treatment, Protective Inoculation. 489 



tion). Experience teaches that these procedures, when applied 

 within the, first quarter of an hour after the bite, will often suc- 

 ceed in postponing an attack of rabies, while later the result 

 becomes more and more uncertain, according to the length of 

 time passed after the bite. 



A favorable result of the treatment, however, no matter 

 how soon it has-been applied, can never be predicted with cer- 

 tainty and, therefore, the bitten animals, in spite of the treat- 

 ment, must be considered as suspicious, they should be placed 

 under careful observation and also be subjected to a protective 

 vaccination (see p. 491). Dogs and cats should be destroyed 

 as soon as possible upon reasonable suspicion of infection. 



The treatment with radium rays studied by Tizzoni & Bougiovanni seems, 

 according to investigations by Calabrese, Danysz, and Ehens, to be of little value 

 from tests on rabbits, and it can hardly be applied to domestic animals. 



Protective Inoculation. The disease which develops in dogs 

 injected with rabies virus may in rare cases come to a stop, and 

 finally a complete cure may be effected. Such recovered cases 

 cannot be infected later with rabies even with large doses of 

 virus, the disease having immunized the organism against the 

 virulent infection. This fact was first, and almost at the same 

 time ascertained by Pasteur and Azary, and, on account of the 

 favorable results of the experiments, Pasteur later introduced 

 an efficient method of anti-rabies vaccination. 



First of all, he ascertained the important fact (1884) that 

 the virus, through artificial transmission from dog to monkey 

 and then further to other monkeys, is gradually so attenuated 

 that it does not any longer cause rabies in dogs, but makes them 

 immune against a later artificial infection with unattenuated 

 virus. On the other hand, the virulence may be increased by 

 repeated passage through the bodies of rabbits and guinea 

 pigs. The increased virulence manifests itself by the fact that 

 material originating from later generations injected subdurally 

 in rabbits will cause rabies after a considerably shorter period 

 of incubation. 



The rabies virus, in the shape in which it is obtained from 

 animals infected in a natural way (street rabies), is inconstant 

 sihce animals infected with it contract rabies after periods 

 of incubation which vary in their duration. Transmitted 

 through bodies of rabbits and guinea pigs, the effect on the ani- 

 mals is not only increased, but also becomes so constant that 

 the spinal cord from the 25th rabbit regularly causes symptoms 

 of rabies on the 8th day, that from the 50th on the 7th, and that 

 from the 90th on the 6th day. Virus that has been thus strength- 

 ened also keeps this quality later on, wherefore Pasteur desig- 

 nates it as "fixed virus of rabies." (Later, Hogyes has reduced 

 the period of incubation to 5 days by using young rabbits for the 

 series of injections.) 



