SMALLPOX 309 



so on through a series of five children, after which all were inoculated 

 with smallpox virus without a single case developing. So con- 

 vincing were Jenner's experiments that within a year or two such 

 vaccination became extensively practiced all over Europe. It is 

 said to have been introduced into the United States in July, 1800, 

 by Dr. Benjamin Waterhouse, Professor of Physic at Harvard 

 University, who vaccinated his own children. 



Jenner and his supporters met with bitter opposition, and even 

 now, more than one hundred years later, there are still to be found 

 opponents to cowpox vaccination, notwithstanding the fact 

 that its systematic application would soon eradicate smallpox from 

 the list of human diseases. 



The relationship of smallpox (variola) to cowpox (vaccinia) 

 has been the subject of a great deal of controversy since Jenner's 

 time, yet no adequate explanation has been found. According 

 to the general belief the smallpox virus, whatever it may be, is 

 so modified by its passage through a lower animal that it loses 

 forever its power of producing smallpox, yet it still retains the 

 ability to provoke the production of antibodies protective against 

 the disease. 



In sections of skin from both variola and vaccinia microscopic 

 cell inclusions were first described by Guarnieri in 1892. These 

 " vaccine bodies " are thought by certain investigators to be 

 protozoan in character and to be closely associated with the 

 cause of both variola and vaccinia ; other authorities regard them 

 as degenerative products. 



As yet all attempts to obtain growth of the virus on artificial 

 culture media has been unsuccessful. A few investigators have 

 reported that the virus is filtrable ; others have failed after re- 

 peated efforts to obtain an infective filtrate. 



During the early days of Jennerian vaccination it was custom- 

 ary to inoculate with the material taken from the pustules of 

 those previously vaccinated with cowpox lymph. The procedure 

 served the purpose of immunization but it had several drawbacks, 

 the chief of which was the danger of transmitting syphilis. For 

 many years now it has been the custom to employ only vaccine 



