MODES OF DISTINGUISHING THE SPIRILLUM. 421 



Further experiments are necessary to show what the 

 exact worth of this reaction is, but extensive observations 

 made up to the present time, especially those of Dunbar 

 conducted on a large series of spirilla, are on the whole 

 distinctly in favour of Pfeiffer's statement being a general 

 law. This method makes the effects of the vital activity of 

 the organism the criterion for distinguishing it from others, 

 and, so far as the production of the disease is concerned, 

 this appears quite rational. It still remains to be seen how 

 far distinction by this means corresponds with differences 

 in cultures. Difficulties may arise when the cholera organ- 

 ism has been grown for a long time outside the body and 

 has lost its virulence. 



Properties of the Serum of Cholera Patients and Con- 

 valescents. Lazarus was the first to show that the serum of 

 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 experiments have been confirmed by 

 Klemperer, Issaeff, and Pfeiffer, and the last mentioned 

 found that the serum of such patients gave the character- 

 istic reaction if injected with the vibrios 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 or two 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. 



