204 PROTECTIVE INOCULATIONS. 



diphtheria. It is precipitated by alcohol, acids, and by magnesium 

 sulphate. 



Finally, Westbrook, in a still more recent research (1894), arrives 

 at the conclusion that the cholera spirillum produces various toxio 

 proteids which in small amounts produce immunity in susceptible 

 animals, and the production of which depends to a certain extent 

 upon the culture medium ; or that its toxin is a substance of constant 

 chemical composition which is mixed with various albuminous sub- 

 stances, either contained in the culture medium or developed in the 

 culture. Duclaux is of the opinion that the last supposition is cor- 

 rect, and that the so-called toxalbumins are not bodies of definite 

 chemical composition, but mixtures of toxins and albuminous sub- 

 stances. 



Experiments made upon the lower animals show that the intro- 

 duction of these cholera toxins into the body of a susceptible animal, 

 either with or without the living cholera spirillum, results in the 

 establishing oi: a certain degree of immunity against the toxic action 

 of cholera cultures . And there is good reason to believe that a non- 

 fatal attack of cholera in man gives the individual a relative immunity 

 from subsequent attacks, for some time at least. This has led to ex- 

 tended experiments with reference to the possibility of producing a 

 similar immunity in man by means of protective inoculations. The 

 experiments bearing upon this point which have been made upon the 

 lower animals will first engage our attention. 



Hueppe (1887) first demonstrated the fact that injection of a small 

 amount of a cholera culture into the peritoneal cavity of a' guinea-pig 

 is fatal to these animals. 



In the following year (1888) Gamaleia reported his success in in- 

 fecting guinea-pigs by subcutaneous injections of blood from an in- 

 fected pigeon. He found that by successive inoculations in pigeons 

 a considerable increase in virulence is established; and that while 

 guinea-pigs were not fatally infected by subcutaneous inoculations 

 with ordinary cultures, they invariably died when inoculated with the 

 more virulent culture in the blood of an infected pigeon. Also, that 

 when guinea-pigs were inoculated with ordinary cultures, or with 

 cultures sterilized by heat, they were subsequently immune, and re- 

 sisted inoculations with the most virulent material. In the same 

 year the author referred to announced the discovery of a spirillum 

 which closely resembles the cholera spirillum his "Yibrio Metch- 

 nikovi." This was obtained from the intestinal contents of fowls 

 suffering from a fatal infectious malady (in Odessa). According to 

 Gamaleia, chickens and pigeons which have survived an inoculation 



