394 CHOLERA. 



obtained by means of capillary glass tubes inserted into 

 the peritoneum) is examined microscopically after a few 

 minutes. If the spirilla injected have been cholera spirilla, 

 it will be found that they become motionless, swell up 

 into globules, and ultimately break down and disappear 

 positive result. If they are found active and motile, then 

 the possibility of their being true cholera spirilla may be 

 excluded negative result. In the former case (positive 

 result) there is, however, still the possibility that the 

 organism is devoid of pathogenic properties and has been 

 destroyed by the normal peritoneal fluid. A control ex- 

 periment should accordingly be made with .001 c.c. of 

 normal serum in place of the anti-cholera serum. If no 

 alteration of the organism occurs with its use, then it is 

 to be concluded that the organism in question has been 

 demonstrated by the specific reaction to be the cholera 

 spirillum. Bordet, and Gruber and Durham, have since 

 devised methods by which a corresponding reaction can 

 be observed outside the body (see Chap. XIX.). 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. Diffi- 

 culties may arise when the cholera organism has been 

 grown for a long time outside the body and has lost its 

 virulence. 



Properties of the Serum of Patients Convalescent from 

 Cholera. 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 



