194 ACTIVE IMMUNIZATION 



cords gradually, when the fifth-day cord is reached a fifth-day cord 

 may be given again as the next day's injection; so also with the 

 fourth-day cord, but after this reduplication the course of the in- 

 jections is resumed and maintained in daily succession, fifth-day 

 cord, fourth-day cord, third-day cord, and over again until the 

 twenty-first day has passed, the dose being 2 c.c. each time" (Keirle). 



Regarding the modus operandi of the antirabic vaccination our 

 knowledge is as yet imperfect, but it appears that as a result of 

 the immunizing process rabicidal substances are formed which are 

 capable of destroying the rabic virus. Babes accordingly combines 

 the active immunization with the passive process, i. e., the intro- 

 duction of the serum of immunized animals, and apparently with 

 satisfactory results. As rabicidal serum has no marked antitoxic 

 properties, and as the symptoms of rabies are evidently toxic in 

 origin, it is clear that no special benefits can be expected from its 

 use when once the disease has developed. 



Results. So far as the results of the antirabic treatment are 

 concerned an analysis of 31,330 cases, in which the existence of 

 rabies in the biting animal had either been definitely established 

 or rendered highly probable, shows an average mortality of but 

 0.75 per cent., which, no doubt, could be still further reduced if the 

 treatment of the bitten persons could always be instituted in time. 



After the disease has once developed, vaccine treatment is, of 

 course, without avail; at present we can only hope that the future 

 may yet teach us some method by which the disease when already 

 in actual progress may yet be conquered and those unfortunates 

 be saved from their terrible sufferings. 



Modifications of the Pasteur Method. In lieu of the technique out- 

 lined above, Harris has recently suggested the following procedure: 

 The brain and spinal cord of the infected rabbit is frozen in carbon 

 dioxide snow, pulverized in this condition, and then dried over 

 sulphuric acid in the vacuum at a temperature of 15 to 18 C. 

 When perfectly dry it is placed in glass tubes which are sealed and 

 stored in the ice-box. In this form the material will maintain its 

 activity for a long time, and after 500 days is still two and a half 

 times as active as three-day spinal cord prepared according to 

 Pasteur's method. 



Since virulent virus is reached relatively late when immunizing 

 according to Pasteur's method, some recent authorities have advo- 



