78 IMMUNITY 



Vaccination Against Small-pox 



Jenner's observations in 1794 established the etiological rela- 

 tionship between human variola and cow-pox. Human small- 

 pox virus passed through a cow will lose its power to produce 

 typical variola but will produce in man a local condition called 

 vaccinia which, upon recovery, leaves behind immunity to 

 variola. 



By the term vaccination, in its strict sense, we mean the applica- 

 tion of attenuated small-pox virus, weakened by passage through 

 kine, to human beings and infecting them with the modified 

 disease. The disease is localized at first at the site of inoculation, 

 and a bleb or vesicle forms. As a rule the disease does not become 

 generalized. It creates, in the vaccinated individual, an active 

 immunity against small-pox. The toxins diffused through the 

 blood-stream stimulate the cells of the body into forming either 

 anti-toxic or other anti-bodies. These various substances, as 

 yet unknown, remain for a long period within the body of the 

 vaccinated person and may protect it for years against invasion 

 and infection with the cytorcytes in virulent form. A person who 

 has variola cannot be vaccinated, subsequently he is immunized 

 against vaccinia by this attack of variola, just as he can^be immun- 

 ized against variola by vaccinia infection. 



Since Jenner first discovered that cow-pox introduced into the 

 body prevented small-pox, it has been the world- wide custom to 

 use either the dried virus or liquid glycerinized virus from the cow 

 or human beings in the process of vaccination. It has been found 

 that human virus generally used was likely in rare instances to 

 transmit syphilis, so it is now the universal custom to use cow 

 virus. This virus is collected from fresh vesicles in calves or 

 young heifers, as clean as possible, as it is used as seed to inoculate 

 the animals and the operation is done under strict antiseptic 

 precaution. After a week the virus is collected under similar 

 antiseptic precautions by scraping the base of the vesicle with a 



