IMMUNITY. 175 



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 one per cent.* 



In all cases where a human being has been bitten by a dog 

 that is suspected of having hydrophobia the individual should 

 submit himself to the Pasteur treatment as soon as possible, 

 if it is feasible to do so. In order to find out whether the dog 

 has hydrophobia, the animal should be killed and the medulla 

 or the head sent to some one competent to make the exam- 

 ination. The examination consists in looking for the Negri 

 bodies and in subdural inoculation of rabbits. If the cord 

 of the dog can be obtained, the intervertebral ganglia will 

 show round-cell infiltration. It is safer not to wait for the 

 examination if the dog is probably mad, though there is abun- 

 dant time usually even to wait for the results of the inoculation 

 of rabbits; still this is not to be recommended. f 



Great care must be taken that the operator may not acci- 

 dentally infect himself. 



Antitoxins. — The first efforts to point out the way along 

 which antitoxins may be produced were made by Salmon and 

 Smith in 1886. In their experiments pigeons were injected 

 with filtrates from cultures containing the products resulting 



* See Ravenel and McCarthy. University oj Pennsylvania Medical Bulletin. 

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

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

 Industry. 



t Varanus A. Moore . Infectious Diseases of Animals . 



