IMMUNITY. 207 



Omitting all but the chief details, the vaccines against 

 hydrophobia are prepared as follows:* 



The cord of a rabbit dead from the subdural inoculation 

 of virus fixe is hung up in a long glass cylinder in the bottom 

 of which is placed potassium hydrate. The cylinder is placed 

 in a cool place, and every day small bits of the cord are cut 

 off and preserved in a vial of glycerin. The virus which has 

 been dried for thirteen or fourteen days is no longer capable of 

 producing hydrophobia in rabbits, but an animal inoculated 

 with it can withstand inoculation with the cord dried for a 

 shorter time, and after inoculation with the latter withstands 

 inoculations with cord dried for a still shorter time. 



In human beings it is customary to start with the virus which 

 has been dried for nine or ten days, injecting subcutaneously 

 emulsions of the dried cord, and, if time permits, to give an 

 inoculation every day with virus dried for a shorter and shorter 

 time. As the incubation period for human beings bitten by a 

 mad dog is quite long, about six or eight weeks, there is 

 ample time to run in all the inoculations if these are begun 

 promptly, and if in this way the individual is made to with- 

 stand the virus fixe, it is more than probable that the weaker 

 virus from the dog will not be able to cause any disease. 



Where much time has elapsed after the bite of the mad 

 dog, it is sometimes the practice to give three or more injections 

 of increasing strength every day. 



These inoculations against hydrophobia have proved 

 to be most valuable, as the large number of reports from various 

 Pasteur institutes in various parts of the world abundantly 

 prove. According to statistics, collected by Ravenel, based on 

 many thousands of cases, the mortality from rabies in those 

 so treated is less than i per centj 



* Valuable information in regard to the preparation and mode of using hydro- 

 phobia virus was contributed in a personal letter to Dr. Williams by Dr. Jas. G. 

 Cummings, Pasteur Institute, University of Michigan. 



fSee Ravenel and McCarthy. University of Pennsylvania Medical Bulletin. 

 June, 1901. Also editorial in Phildelphia Medical Journal. March 14, 1903. 

 And Mohler. Twelfth Annual Report of the United States Bureau of Animal 

 Industry. 



