HYDROPHOBIA. 309 



a large nerve-trunk or into a peripheral nerve. Rabies has, 

 however, followed absorption of the virus by an intact mucous 

 membrane, such as that of the nose, or the conjunctiva, or the 

 genitalia, or the digestive tract. Intravenous injection always 

 is followed by positive results. Intra-uterine infection is also 

 possible. The nervous system of an animal dead of rabies 

 contains a sufficient quantity of virus to produce the disease 

 when these tissues are injected into other animals. 



Vitality : The virus is extremely resistant to chemicals and 

 temperature. An exposure of one hour to a temperature of 

 50 C. is necessary to destroy the virus. A 5 per cent, solu- 

 tion of carbolic acid is destructive in fifty minutes. The 

 same is true of a 1 : 1000 bichloride solution and a 5 per 

 cent, potassium permanganate solution. The desiccated spinal 

 cord of an animal dead of hydrophobia retains its virulence 

 for two weeks. 



Immunization: The treatment of rabies, aside from the 

 treatment of recent and single wounds, which is surgical, is 

 limited almost entirely to preventive inoculation with hydro- 

 phobic serum. Pasteur began by inoculating animals with 

 preparations of spinal cords possessing only a slight degree 

 of virulence, and gradually increased the virulence of the 

 injection until he succeeded in producing immunity, which 

 protected the animal against a quantity of virus that would 

 invariably kill an unprotected animal. 



In order that the treatment may be a success, it is abso- 

 lutely necessary that the patient come under the observation 

 of a physician as soon after the injury as possible. Usually 

 people are inclined to temporize and see whether or not any- 

 thing will happen to the victim. After the symptoms of the 

 disease have appeared it is too late. 



The serum which is used for " curative " purposes consists 

 of an emulsion of the rabbit's spinal cord which has been 

 dried over caustic potash for from seven to ten days. The 

 first injection, which is made subcirtaneously, consists of 

 about two grams of this emulsion. This dose is repeated 

 every day for twenty-five days. For each successive injec- 

 tion an emulsion is used which is made from a cord which 

 has not been dried so long, and which contains a more viru- 



