IMMUNIZATION AGAINST HYDROPHOBIA 87 



indicated by lacrimation and purulent collections within twenty- 

 four hours. Mallein has been used as a prophylactic agent 

 against glanders with some success, and treatment can be carried 

 on with it in valuable animals. 



Immunization Against Hydrophobia 



While the actual causal agent of hydrophobia has thus far 

 eluded bacteriologists, certain well-marked histologic lesions have 

 been discovered in the ganglia of the central nervous system, and 

 in the medulla, which are not found in any other disease. This 

 dispels all doubt as to the fact that hydrophobia is a real clinical 

 entity. 



It is possible to immunize animals and man against this disease 

 by the use of attenuated virus. In common with many other 

 viruses, that of hydrophobia can be weakened through the action 

 of either heat, drying, light, or chemicals. Pasteur found that by 

 drying the spinal cords of rabid animals for two weeks, they be- 

 come totally avirulent. If the cord is dried but three or four days, 

 the virulence is but slightly reduced. Immunity to rabies can be 

 produced by injecting minute quantities of the poison, and then 

 gradually increasing the dose until virulent virus can be employed. 



Recent work seems to indicate that simple dilutions of the 

 virus so that minute quantities are used, can be employed 

 prophylactically instead of dried material. . ' 



Modification of the amount of poison used may be affected by 

 employing equal quantities of spinal cords from rabid animals that 

 have dried varying lengths of time. The vaccine consists of pieces 

 of cord, i cm. in length, from rabbits that have been killed by 

 inoculation with fixed virus. This is emulsified with sterile salt 

 solution. Cord that has dried for fourteen days is first injected, 

 after which cords that have dried fewer and fewer days, until, 

 finally, one that has dried only three days is injected. 



In cases of bites by rabid dogs on the face or head, the vaccina- 

 tion must be rapid, so two injections per diem are given. In 



