372 IMPORTANT VARIETIES OF FISSION-FUNGI. 



a school of fish, according to Koch) speaks strongly in favor of 

 cholera, for vibrios resembling those of cholera, if present in the 

 stools at all, are usually only scanty. If the stool is of nearly nor- 

 mal consistency, the direct microscopic examination may be omitted. 

 One should avoid mistaking the thin spirilla (Sp. hachaizae) for vibrios. 



2. Testing of a fresh, minimal specimen of the stool which con- 

 tains living vibrios in great number with serum, as on page 373. 



3. Infection of an alkaline peptone chlorid of sodium solution l 

 (about 50 c.c.) with a flake of mucus or with 1 to 5 c.c. of the stool. 

 This is to be kept at incubator temperature. (Preliminary cholera 

 culture.) 



(a) Observation of the pellicle formation. After three hours indica- 

 tion of pellicle formation may be present. After about sixteen to 

 twenty-four hours the pellicle does not become more distinct. (Many 

 micro-organisms form pellicles ! ) 



(6) Microscopic demonstration of vibrios in pellicles. Here the 

 occurrence of vibrios demonstrates much less the presence of true 

 cholera vibrios than does a large number in the stool. Also vibrios 

 resembling cholera may develop into pellicles. 



(c) Agar plates from the pellicle (37) after eighteen hours must 

 not be phosphorescent. 



(d) Gelatin plates from the pellicle (22). After sixteen to twenty- 

 four hours, when magnified sixty times, the characteristic shining and 

 coarsely granular colonies are found. The form of the growth in 

 gelatin is one of the principal characteristics. The suspicious colonies 

 (if not numerous, all are considered ) are inoculated as soon as practic- 

 able into gelatin (flattened funnel-shaped liquefaction) and tubes of 

 peptone chlorid of sodium solution (indol reaction). 



(e) Indol reaction (without nitrite being added) with part of the 

 tubes after three hours. The indol reaction is usually certainly present 

 in cholera after eighteen hours. By rapid transformation of the 

 nitrite into ammonia, various water bacteria can frustrate the direct 

 cholera reaction. See page 359 regarding the failure of the indol 

 reaction in pure cultures of certain cholera. 



(/) Potato cultures from the pellicle. Chlorid of sodium potato 

 (p. 357) at 37. Yellowish-brown to brownish-red color is in favor of 

 cholera. 



4. Gelatin plates prepared directly from the stool (3 dilutions). 

 Abundant colonies of vibrios with a form like those of cholera speak 

 very strongly for cholera even if the liquefaction appears too vigor- 

 ous. 



5. Agar plates smeared over very thinly with very much diluted 

 stool and kept at 37. Photogenic colonies are not looked upon as 

 cholera. 



6. All vibrios isolated in these ways must be examined with the 



1 For the preliminary cholera culture, in order to produce energetic 

 alkalinization, there is always added to 100 c.c. of nutrient medium, 

 neutralized with phenolphthalein, 2 c.c. of normal sodium hydroxid 

 or \% crystalline or 0.3% anhydrous soda, in which way many water 

 bacteria are eliminated. 



