RABIES OR HYDROPHOBIA 229 



infection with cow-pox will give resistance to human 

 smallpox. Vaccination was formerly practised by 

 transferring the pox from person to person, but now 

 fresh material is used from a cow which has been 

 artificially infected with smallpox. By passing this- 

 virus through the calf it is so altered that it cannot 

 produce smallpox in man yet it can, when inoculated 

 into the skin, call forth an immunity against subsequent 

 infection with that disease. Jenner, in 1798, was the 

 one who first developed the principle of using cow-pox 

 in the protection against human variola. The exact 

 cause of smallpox is not known. It is supposed to 

 spread by contact either directly with the sick or 

 indirectly by objects having been in contact with them. 

 Such objects are called fomites. Bacteria are present 

 in the pustules caused by vaccination and in the 

 eruption of smallpox, but they have been proven to 

 be secondary invaders. 



Rabies or Hydrophobia. This is an acute infectious 

 disease to which nearly all animals are susceptible, 

 characterized by slowly progressive palsies and deli- 

 rium. Hydrophobia means fear of water. Such an 

 emotion does not exist, but animals merely avoid 

 water because they cannot swallow it. The cause of 

 rabies is excreted in the saliva and may be transmitted 

 by the bite of a rabid animal, or by getting the saliva 

 into an open wound. The virus is innocuous if 

 swallowed. After having entered the body the virus 

 travels to the central nervous system and remains 

 there throughout the whole attack. The spinal cord 

 particularly is involved. The only evidence there is 

 of the actual causative germ is the presence of minute 



