HUMAN EXPERIMENTS. 419 



the rapid fall of temperature being a striking feature. They 

 found that the toxicity of the filtrate was not altered by boiling. 

 It is somewhat difficult to reconcile the results of Pfeiffer and 

 Metchnikoff as regards the action of heat, and there is evidence 

 that the toxic substances present in the bodies of the spirilla 

 differ from those present in filtered cultures. A considerable 

 number of observers, however, agree in stating that, at least 

 some toxins obtained from cholera cultures are not destroyed at 

 100° C. 



A great many observers have attempted to obtain toxins in a chemically 

 pure condition, but so far without results which can be regarded as conclusive. 

 Hueppe and Wood found that the most active toxins were produced by 

 growing the cholera' organism in albumin in anaerobic conditions, and con- 

 sidered that this corresponded to the mode of their production in cholera. 

 SchoU confirmed Hueppe's results, and obtained from cultures under such 

 conditions a peptone which possessed highly toxic properties, and which he 

 called cholera toxo-peptone. These results, however, have been adversely 

 criticised by various observers. Wesbrook obtained different substances 

 according to the media on which the cholera organisms were grown, and yet 

 these produced very much the same effects, chiefly collapse, subnormal 

 temperature, cramps, dyspnoea, etc. Such toxic bodies were even obtained 

 from cultures in asparaginate of soda solution, which did not contain any 

 proteid substance. He therefore came to the conclusion that the so-called 

 toxalbumins, etc., are really mixtures of albumins and true toxins, the 

 chemical nature of the latter not having been yet determined. Wesbrook 

 also obtained the toxic bodies in small quantity from the pleural exudate of 

 guinea-pigs killed by the vibrio. Bosc also found that the blood, and to a 

 less extent the urine, of patients who had died in the algid stage, produce 

 toxic phenomena and death, when injected intravenously in rabbits. In this 

 case also, nothing is known with regard to the chemical nature of the toxic 

 bodies. 



Experiments on the Human Subject. — Experiments have also 

 been performed in the case of the human subject, both intention- 

 ally and accidentally. In the course of Koch's earlier work, one 

 of the workers in his laboratory shortly after leaving was seized 

 with severe choleraic symptoms. The stools were found to 

 contain cholera spirilla in enormous numbers. Recovery, how- 

 ever, took place. In this case there was no other possible 

 source of infection than the cultures with which the man had 

 been working, as no cholera was present in Germany at the time. 

 Within recent years a considerable number of experiments have 

 been performed on the human subject, which certainly show that 

 in some cases more or less severe choleraic symptoms may follow 



