IMMUNITY. 1 7 



demonstration of the protective value of vaccination, but in 

 1840 it was prohibited by an act of Parliament. 



There is some evidence that vaccination as a protection 

 against smallpox was practised to a limited extent prior to the 

 time of Jenner. Thus Von Humboldt has stated that it was 

 known at an early period to the Mexicans. But its introduc- 

 tion as a reliable method of protecting against smallpox is due 

 to the patient researches of the renowned English physician, 

 whose attention was first attracted to the subject in 1768, 

 although it was not until 1796 that he made his first vaccina- 

 tion in the human subject. His first public institution for the 

 practice of vaccination was established in 1 799, and the follow- 

 ing year the practice was introduced into France, Germany, 

 and the United States. 



In the infectious disease of cattle known as pleuropneumonia, 

 protective inoculations were successfully made some time 

 before the demonstration by Pasteur of the efficacy of such 

 inoculations in anthrax and chicken cholera (1880). Various 

 methods have been employed. Thus Willems states that the 

 natives of the banks of the Zambeze cause animals to swallow 

 a certain quantity of the liquid from the -pleura! cavity of an 

 animal recently dead, and thus give them immunity. The 

 virus has been injected into the circulation by some experi- 

 menters, and others have proposed to attenuate it by heat. 

 But the method which has been most extensively employed is 

 that discovered by the Dutch settlers at the Cape of Good 

 Hope (the Boers), and consists in inoculating animals in the 

 tail with serum from the lungs of an animal recently dead, or 

 with a virus obtained from the tumefaction produced by such 

 an inoculation in the tail. This secondary virus was very 

 extensively used by Lenglen, a veterinarian at Arras, who 

 communicated his results to the Academy of Science at Paris, 

 in April, 1863, and Willems says, in his last published commu- 

 nication, that this is the method which he prefers. It is also 

 the method most extensively employed in Australia, into which 

 country infectious pleuropneumonia was introduced in 1858. 



Toussaint, a pioneer in researches relating to protective 

 inoculations, has a short paper in the Comptes-Rendus of the 



