420 CHOLERA. 



ingestion of pure cultures, whilst in others no effects may result. 

 The former was the case, for example, with Emmerich and 

 Pettenkofer, who made experiments on themselves, the former 

 especially becoming seriously ill. In the case of both, diarrhoea 

 was well marked, and numerous cholera spirilla were present in 

 the stools, though toxic symptoms were proportionately little 

 pronounced. Metchnikoff also, by experiments on himself and 

 others, obtained results which convinced him of the specific re- 

 lation of the cholera spirillum to the disease. Lastly, we may 

 mention the case of Dr. Orgel in Hamburg, who contracted the 

 disease in the course of experiments with the cholera and other 

 spirilla, and died in spite of treatment. It is believed that in 

 sucking up some peritoneal fluid containing cholera spirilla, a 

 little entered his mouth and thus infection was produced. This 

 took place in September 1894 at a time when there was no 

 cholera in Germany. On the other hand, in many cases the 

 experimental ingestion of cholera spirilla by the human subject 

 has given negative results. Still, as the result of observation of 

 what takes place in a cholera epidemic, it is the general opinion 

 of authorities that only a certain proportion of people are 

 susceptible to cholera, and the facts mentioned above have, in 

 our opinion, great weight in establishing the relation of the 

 organism to the disease. 



Immunity. As this subject is discussed later, only a few 

 facts will be here stated, chiefly for the purpose of making clear 

 what follows with regard to the means of distinguishing the 

 cholera spirillum from other organisms. The guinea-pig or any 

 other animal may be easily immunised against the cholera 

 organism by repeated injections (conveniently made into the 

 peritoneum) of non-fatal doses of the spirilla. It is better to 

 commence the process with non-fatal doses of cultures killed by 

 the vapour of chloroform or by heat, the doses being gradually 

 increased, and afterwards to proceed with increasing doses of 

 the living organism. In this way a high degree of immunity 

 against the organism is developed, and further, the blood 

 serum of an animal thus immunised (anti-cholera serum) 

 has markedly protective power when injected, even in a small 

 quantity, into a guinea-pig along with five or ten times the 

 fatal dose of the living organism ; it has also the property 

 of agglutinating the cholera organism. These properties, 



