VACCINATION. IMMUNIZATION. INOCULATION 233 



ism decreases with its continued cultivation on artificial culture 

 media. The anthrax bacillus especially progressively decreases 

 in virulence with long-continued cultivation (see Pasteur's 

 vaccination process) and finally loses its virulence altogether. 

 Similar observations have been made in connection with the con- 

 tagion of chicken cholera, lung plague, pox and other infectious 

 diseases. 



8. The passage of the infectious material through the bodies 

 of animals of another species. The inoculation of some infec- 

 tious materials into animals of a different species has the effect 

 of modifying their virulence. Best known in this respect is the 

 inoculation of cattle with the virus of pox of man and the re- 

 inoculation of man with the considerably attenuated virus thus 

 obtained (cow pox vaccination of Jenner). A similar effect is 

 obtained by the same process with the virus of rabies (monkeys, 

 rabbits), swine erysipelas, tetanus and diphtheria of man (horses, 

 rabbits), anthrax and black leg (sheep, goats, horses) and also 

 in other diseases. 



The Different Methods of Vaccination. — ^According to the 

 part of the body into which the infectious material is injected, 

 the following methods of vaccination are distinguished: 



1. The cutaneous or endermatic vaccination consists of a super- 

 ficial wounding of the epidermis of the skin and exposing the 

 deeper layers of the rete malpighii. By no means must the wound 

 extend to the subcutis. The vaccination is carried out with a 

 vaccination lancet or needle in such a manner as to avoid bleeding 

 if possible. A flow of blood will wash the infectious material off 

 the skin. Cutaneous vaccination is used for foot-and-mouth 

 disease, sheep pox and small pox of man. Corresponding to the 

 cutaneous method is the mucous membrane vaccination, in which 

 there is only a superficial wounding of the epithelium, the sub- 

 mucosa being avoided; cattle are vaccinated for foot-and-mouth 

 disease upon the mucous membrane of the mouth. Vigorous 

 rubbing of the mucous membrane is sufficient to wound it super- 

 ficially. Corneal vaccination is also included in the term cutaneous. 



