MAN'S FIGHT FOR SURVIVAL 631 



of attacking personal liberty, a serious legal problem is involved in 

 their control. 



In order to stamp out parasitic diseases absolutely, there must be 

 effective control of the activities of carriers. This is a difficult matter 

 to carry out because of the injustice worked on the carrier who fre- 

 quently must make a living. Perhaps medical discoveries will find 

 some way to make carriers safe, but at least they must be educated 

 as to their potential danger to others. Upon their co-operation, the 

 health of a community frequently depends. 



Vaccines and Attenuated Organisms 



The story of the use of vaccines in the fight against germ disease is 

 tied up closely with the work of Louis Pasteur. In 1880, while he was 

 engaged in an investigation of chicken cholera, several virulent cul- 

 tures of cholera bacteria were overlooked and left in the laboratory. 

 Some days later these organisms were used to inoculate healthy fowls. 

 To Pasteur's surprise the birds did not die and later were found to 

 be immune to the deadly chicken cholera germs. This discovery 

 gave Pasteur the idea of using weakened or attenuated cultures of 

 bacteria in inoculation as a protection against disease. Continued 

 study showed that anthrax, if grown in the laboratory at a relatively 

 high temperature, was also much weakened and could be used suc- 

 cessfully in inoculation against anthrax in sheep and cattle. 



The same idea was used in Pasteur's famous and successful attack 

 on rabies. It is a dramatic episode worth the telling. Rabies, a dis- 

 ease of dogs transmissible to man, had long been known as a dread 

 and incurable enemy of mankind. Pasteur first unsuccessfully tried 

 to make vaccine from the saliva of rabid dogs, but later found that, 

 since the disease attacks the central nervous system, the dried nerve- 

 cord of infected animals gave him a source for the inoculating virus. 

 He dried nerve cords of infected rabbits for a period of fourteen days 

 and found that by that time the organism had lost its virulence so that, 

 when inoculated into dogs, it had no effect. Beginning with cords 

 dried for thirteen days and continuing inoculations made from crushed 

 fragments of cords which had only dried one day, Pasteur was able 

 to prove that dogs bitten by other rabid dogs w^ere protected against 

 the disease. But to carry this experiment over to human beings was 

 another matter. Ultimately a small boy from the province of Alsace, 

 terribly lacerated by a mad dog, was brought to his laboratory. It 

 was a life or death case and Pasteur made the inoculations with fear and 



H. W. H. 41 



