QUALITATIVE BACTERIOLOGICAL ANALYSIS. Ml 



loopful (1*5 mgm.) of a young agar culture be added to 1 c.c. of 

 broth, and the mixture then injected into the peritoneal cavity 

 of a guinea-pig, weighing 300350 grammes. The weight of the 

 animal must always be taken into consideration ; if a guinea-pig 

 of greater weight is employed for the experiment a larger dose 

 of the agar culture must be given. One or two hours after the 

 injection the animal is languid, loses its appetite, and there is a 

 rapid fall of the body temperature, sometimes preceded by 

 pyrexia, and death ensues from collapse. Koch states that none 

 of the spirilla which can possibly come into question during the 

 investigation of cholera, when employed in the above dose, give 

 rise to the same symptoms as the true cholera spirilla. 



According to Metchnikoff both the indoi reaction and the 

 virulence test are open to question. Sanarelli and Kohlbrugge 

 have both isolated from water supplies vibrios which give the 

 cholera-red reaction; indeed Kohlbrugge's investigations appeared 

 to show that temperature and season of the year had an influence 

 on this reaction. 



It is thus evident that the diagnosis of the cholera spirillum, 

 ordinarily fairly easy when the microbe is isolated from a case of 

 cholera, may be exceedingly difficult, owing to the variability of 

 its reactions, when it has gained access to water. Klein has 

 shown how modifications of the cholera vibrio can be artificially 

 induced. He inoculated non-sterile sea- water with an agar 

 culture of a St. Petersburg cholera vibrio, and then isolated it 

 again eleven days later. The vibrio was found to have under- 

 gone the following modifications : 



(a) It had lost altogether its power of growing at 37 C. either 

 on agar or in peptone. 



(b) It grew at 20 C. in peptone and salt solution, but when 

 tested with pure sulphuric acid, after incubation for four or 

 more days, it gave no trace of the cholera-red reaction. 



(c) In stained specimens it appeared thicker than the St. 

 Petersburg vibrio. 



(d) When injected in considerable doses into the peritoneal 

 cavity of a guinea-pig it produced no diseased condition ; the 

 animal remained well. 



(e) When tested with cholera serum, which quickly agglu- 

 tinated the original St. Petersburg vibrio, it gave a negative 



Q 



