732 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



for the rabbit, the animal shows symptoms on the sixth or seventh 

 day after inoculation. When the virus attains this degree of virulence 

 it is called "fixed virus" and may be used in the preparation of the 

 vaccine. The " fixed virus" or spinal cord of the rabbit which has 

 succumbed to the disease in six or seven days, is removed aseptically 

 and placed in a special drying chamber. The cords are suspended over 

 caustic potash and dried at a temperature of 23 for a period of from 

 one to ten or fifteen days. 



The treatment of the patient consists in the hypodermic applica- 

 tion of the "fixed virus" which has been attenuated by drying. The 

 exact nature of the vaccine used in the initial vaccination and the time 

 consumed in the series of injections depend, to some extent, upon the 

 case in hand. Frequently, the patient is first vaccinated with a sus- 

 pension of a spinal cord which has been attenuated by drying for four- 

 teen or fifteen days. On the succeeding days of the treatment use is 

 made of the suspension of spinal cords, which have been less and less 

 attenuated. The treatment usually lasts about twenty days or until 

 the patient has received an injection of the least attenuated "fixed 

 virus." 



It is very important, when one is bitten by a rabid animal, that the 

 Pasteur treatment be begun as early as possible, in order that active 

 immunity may be secured before the expiration of the incubation period. 

 In many of the larger cities of the United States, for some time, labora- 

 tories have been maintained for the purpose of administering the 

 Pasteur treatment. More recently, commercial laboratories have 

 developed methods of preparation and distribution, so that any phy- 

 sician may purchase the vaccine and administer it to his patients. 



Hogyes* substituted dilutions of the "fixed virus" for the dried 

 spinal cords. For the initial treatment, a few cubic centimeters of a 

 i : 10,000 dilution were used. In the succeeding injections graduated 

 dilutions were employed. While the work of Hogyes has been con- 

 firmed by other investigators, the method is not generally regarded 

 as possessing the safety of the original Pasteur treatment. 



Harris f has devised a simple method of preparing the vaccine by 

 freezing the infected spinal cord of the rabbit with C0% snow, and then 

 drying the material in vacuo over sulphuric acid at a temperature of 

 10 to 15. 



* Hogyes, Acad. des Sciences de Budapest, Oct. 17, 1897. 

 t Harris, Jour. Infect. Dis., 1912, 10, p. 369. 



