360 IMPORTANT VARIETIES OF FISSION-FUNGI. 



peptone and chlorid of sodium, 1 etc. , some nitrate is 

 produced (Petri), indol can be demonstrated by the addi- 

 tion of sulphuric acid alone: "cholera reaction of Dun- 

 ham and Bujwid," nitroso-indol reaction of the authors. 

 After keeping the culture longer the intensity of the reaction 

 increases somewhat up to twenty-four or forty-eight hours; 

 later the nitrite gradually decreases, and, in order to 

 demonstrate the quantity of indol, which increases for 

 some days, some nitrite solution must be added (p. 78), 

 when a dark violet-red color is obtained. A large loopful 

 of an old agar culture will carry sufficient indol into 10 c. c. 

 of peptone water for demonstration. The indol reaction 

 rarely fails. (See p. 372. ) 



(h) Toxins: Manifold poisons have been produced from 

 cholera cultures, but all are much less poisonous than the 

 original material. According to R. Pfeiffer, these poisons 

 are to be conceived as secondary, altered products from 

 the disturbing action of reagents. Much more powerful 

 but qualitatively similarly acting poisons are obtained 

 from the bodies of the vibrios by very careful killing of 

 the pure culture upon agar with chloroform or by brief 

 heating, but the filtrate of young cultures is not 'poison- 

 ous. 2 Three times the quantity (about 0. 5 mg. agar cul- 

 ture) of the minimum fatal dose of living bacteria, after 

 being killed, also kills a guinea-pig in sixteen to eighteen 

 hours. By longer heating the toxicity rapidly decreases. 

 The effects of all these poisons when injected intraperi- 

 toneally are exactly the same as those following the intro- 

 duction of living vibrios into the peritoneum : rapidly 



1 If the peptone and sodium chlorid are absolutely free of nitrate, 

 then a weak solution of nitrate must be added. According to Bleisch, 

 40 drops of a 0.08% solution of saltpeter to 100 of nutrient solution 

 was the proper quantity. If the nutrient medium contains too much 

 nitrate, too much nitrite is supplied and interferes with the nitroso- 

 indol reaction. 



2 Metschnikoff, Roux, and Taurelli-Salimbeni have obtained by 

 means of all sorts of devices, fluid cultures of highly virulent cholera 

 organisms, the filtrates of which were very poisonous. With such 

 toxins also cholera antitoxins can be produced. While Pfeiffer's anti- 

 bacterial serum protects animals very well from intraperitoneal infec- 

 tion, it is entirely without effect against infection through the stomach, 

 against which the antitoxic serum affords some protection (C. B. 

 XX, 627). 



