398 MANUAL OF BACTERIOLOGY. 



The peptone solution is made by taking i part of the 

 enriching fluid described below for the examination of water 

 for the cholera spirillum (p. 399), and diluting with 9 parts of 

 water, distributing it in test-tubes, 10 c.c. in each, and 

 sterilizing. 



At the time that the first smear preparations and gelatin 

 plates are prepared, tubes of peptone solution should be 

 inoculated directly from the intestinal contents, and kept in 

 the incubator (Schottelius). After development has occurred, 

 the production of indol may be tested by the addition of sul- 

 phuric acid. These tubes are especially valuable when un- 

 favorable material or when material containing small numbers 

 of the spirilla is used. In the incubator the spirilla may be 

 expected to multiply in the peptone solution rapidly, and to 

 appear upon the surface of the liquid in large numbers, even 

 forming a visible film in six hours. Smears may be made 

 from the surface part of these tubes, stained, and examined 

 with a microscope. From the same material gelatin plates 

 should be prepared, and examined as soon as the colonies 

 develop. 



Ashburn and Craig* have sounded a warning against too 

 great reliance upon bacteriological results in the early diag- 

 nosis of cholera. It is seldom that even approximately pure 

 cultures of the cholera bacillus are obtained from stools, and 

 from mixed cultures from the stools they obtained the " cholera- 

 red" reaction in one case only. The reaction can usually be 

 obtained in pure cultures by using media prepared with 

 Grubler's peptone, but not with other peptones. 



When cultures are obtained, their effects may be tested 

 upon guinea-pigs, by injecting them into the peritoneum. 



The production of Pfeiffer's phenomenon is at present 

 regarded as the most important and final means of diagnosis 

 between the cholera spirillum and related forms. This con- 



*Journ. Am. Med. Assn. Vol. XL VIII. No. 8. Feb. 23, 1907. p. 692. 



