ROLE OF BATS IN RABIES 225 



brally developing chicken embryos. He soon discovered that all tissues of 

 the embryo supported the virus. Whereas this virus source would not 

 permit the preparation of an inactivated vaccine, the virus strain was 

 avirulent, would not induce rabies by any usual method of inoculation, 

 and was highly immunogenic since a single injection produced complete 

 immunity. This type of vaccine was a great advance over the older types 

 prepared from nerve tissue — brain and spinal cords — from the rabbit, 

 horse, calf, sheep, and goat. Historically, it has been shown that there is 

 a rather high incidence of post-vaccinal paralysis when nerve tissue vac- 

 cines are used, regardless of the method used to inactivate the virus — 

 phenol, chloroform, merthiolate, ultra violet radiation, or just desicca- 

 tion. The cause of paralysis following the injection of nerve tissue has 

 not been conclusively proven. One school of thought is that myelin, a 

 common antigen in all mammalian nerve tissues, injected in volume at 

 the right interval forms antimyelin antibody. The resulting antigen- 

 antibody reaction brings about varying degrees of paralysis and occasion- 

 ally causes death. In one kennel, carefully studied, the incidence of para- 

 lysis was four in one hundred. In man in the city of Los Angeles the in- 

 cidence is one in six hundred. Not a single post-vaccinal reaction has been 

 reported following the use of chicken embryo vaccines. Because it was 

 impractical to distribute a chick embryo live virus vaccine in a frozen 

 state, and since it was unstable in the fluid state, it has been prepared as 

 a dry product — dried from the frozen state and sealed in vacuo. 



TABLE I 



Identity Test of Virus Isolation from Cattle Brains from 



La Ceiba, Honduras 



Mortality ratio of guinea pigs challenged with 

 dilutions of street virus — deaths/total 



NYC strain Honduras strain 



1:5 1:5 1:20 1:80 1:320 1:1280 



Immunized 0/14 0/14 



Controls 10/10 6/10 6/8 8/8 8/8 5/8 



The virus isolated from cattle in the Honduras area was shown to 

 be indistinguishable immunologically from a New York dog salivary 

 gland street-virus strain (Table I). It was therefore proposed that an 



