420 CHOLERA. 



For Haffkine's method of preventive inoculation vide 

 chapter on Immunity. 



Means of Distinguishing the Cholera Organism. 

 According to Koch the most important points in the dia- 

 gnosis of cholera are : 



(a) Microscopical characters of the dejecta. (6) Ap- 

 pearance of the colonies in gelatine plates, (c) Their 

 appearance on agar plates, (d) The growth in peptone 

 solution, (e) The cholera-red reaction. (/) The effect 

 of intraperitoneal inoculation of guinea-pigs with pure 

 cultures. 



There can be no doubt that in the great majority of 

 cases these points taken collectively are sufficient, but 

 in some cases difficulties have arisen. Pfeiffer has accord- 

 ingly introduced the method of diagnosis described above, 

 which depends on the supposed specific action of an anti- 

 cholera serum. Further, he has found that a striking dis- 

 integrative change is observed microscopically in the spirilla 

 when injected along with the protective serum into the 

 peritoneal cavity of another guinea-pig Pfeiffer's reaction. 



The method is as follows : A loopful (2 mgrm.) of recent agar 

 culture of the organism to be tested is added to I c.c. of ordinary 

 bouillon containing .001 c.c. of anti-cholera serum. The mixture is 

 then injected into the peritoneal cavity of a young guinea-pig (about 

 200 grm. in weight), and the peritoneal fluid of this animal (con- 

 veniently 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, how- 

 ever, still the possibility that the organism is devoid of pathogenic 

 properties and has been destroyed by the normal peritoneal fluid. A 

 control experiment 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.). 



