PROPERTIES OF IMMUNE SERUM. 423 



patients who had suffered from cholera possessed the power of 

 protecting guinea-pigs, when injected in very minute quantity 

 along with a fatal dose of the cholera organism. These experi- 

 ments were confirmed by Klemperer, Issaeff, and Pfeiffer, and 

 the last mentioned found that the serum of such patients gave 

 the characteristic reaction if injected with the spirilla into the 

 peritoneal cavity of a guinea-pig. Further, so far as experiment 

 has gone, this action is not exerted against any other organism 

 — that is, it is specific towards the cholera spirillum. This 

 action of the serum may be present eight or ten days after the 

 attack of the disease, but is most marked four weeks after ; it 

 then gradually becomes weaker and disappears in two or three 

 months (Pfeiffer and Issaeff). 



Specific agglutinative properties have, however, been detected 

 in the serum of cholera patients at a much earlier date, in some 

 cases even on the first day of the disease, though usually a day 

 ortwo later. The dilutions used were 1-15 to 1-120, and these 

 had no appreciable effect on organisms other than the cholera 

 spirillum (Achard and Bensande). Needless to say, such facts 

 supply strong additional evidence of the relation of Koch's 

 spirillum to cholera. 



General Summary. — We may briefly summarise as follows 

 the facts in favour of Koch's spirillum being the cause of cholera. 

 First, there is the constant presence of spirilla in true cases 

 of *cholera, which on the whole conform closely with Koch's 

 description, though variations undoubtedly occur. Moreover, 

 the facts known with regard to their conditions of growth, etc., 

 are in conformity with the origin and spread of cholera epidemics. 

 Secondly, the experiments on animals with Koch's spirillum or 

 its toxins give as definite results as one can reasonably look for 

 in view of the fact that animals do not suffer naturally from the 

 disease. Thirdly, the experiments on the human subject and the 

 results of accidental infection by means of pure cultures are also 

 strongly in favour of this view. Fourthly, the agglutinative and 

 protective properties of the serum of cholera patients and con- 

 valescents constitute another point in its favour. Fifthly, bac- 

 teriological methods, which proceed on the assumption that 

 Koch's spirillum is the cause of the disease, have been of the 

 greatest value in the diagnosis of the disease. And lastly, the 

 results of Haffkine's method of preventive inoculation in the 



