NATURAL AJSD ACQUIRED EVIMUNITY 111 



in individuals in order to render them immune. A procedure of 

 protective inoculation (into skin) was introduced into England 

 in 1717 by Lady Montagu who had learned of it while in Con- 

 stantinople. 



In 1798, Jenner published his brilliant discovery that inocula- 

 tion of the human being with vaccinia or cowpox viriLs leads to the 

 development of a la^sting active immunity to the virus of smallpox. 

 Thus was introduced the term vaccination as well as the principle 

 of immunization with an infectious agent of low virulence. 



While at first, vaccination against smallpox encountered great 

 opposition and was fraught with the danger of secondary infec- 

 tion, it has, nevertheless, achieved brilliant results. This is in- 

 dicated by Turgensen's statistics for Sweden, cited by Zinsser 

 and Bayne- Jones (1939). He states that during the 25 years pre- 

 ceding the introduction of smallpox vaccination (1776-1801) the 

 death rate due to this disease was 2,050 per million inhabitants. 

 During the transitional period (1801-1810) it was 680, and after 

 vaccination became compulsory in 1810, it dropped to 169 per mil- 

 lion inhabitants. In the Kansas City epidemic of 1921, there were 

 1,090 cases with 222 deaths. The deaths occurred among non- 

 vaccinated individuals only. 



Great progress has been made in the preparation of a satisfac- 

 tory vaccine. Calves have been used almost exclusively in its 

 preparation although Rivers (1933-1939) states that it is now pos- 

 sible to prepare a vaccine of more assured bacterial sterility by 

 cultural methods. Gallagher and Wolpert (1940) describe a meth- 

 od of vaccine preparation in the rabbit fetus. A comprehensive dis- 

 cussion of methods of vaccine preparation and immunization against 

 smallpox, rabies, and rickettsiae is given by Zinsser and Bayne- 

 Jones (1939) and by Zinsser, Robinson, and other contributors to 

 , the Harvard symposium on virus and rickettsial diseases (1940). 

 While it is generally recognized that living, attenuated virus vac- 

 cines are the most potent ones, yet there are many, according to 

 Zins.ser (1940), who feel that killed virus and killed rickettsiae have 

 .some hnmunizing value providing sufficiently large doses are em- 

 ployed. Veintemillas (1939) reports that the formalin-killed sus- 

 pension of ^Mexican rickettsiae prepared in accordance with the 

 methods of Zhisser and Castaneda (1931) has been found of prac- 



