368 INFECTIVE DISEASES. 



chemical tests which can be applied to cultures. According to 

 Frankel, the Bujwid- Dunham test can be relied upon to distin- 

 guish Koch's comma-bacillus from the comma-bacillus of Finkler - 

 Prior (cholera nostras), and from those found by Gamaleia. The 

 comma-bacilli are inoculated in broth containing peptone, and, 

 after twelve hours in the incubator, a drop of strong sulphuric 

 acid added to the culture will produce a red colour, owing to the 

 presence of indol. A test which distinguishes Koch's comma - 

 bacillus from Finkler- Prior's and Deneke's was introduced by Cahen. 

 A solution of litmus is added to the broth, and the culture placed 

 in the incubator, until the following day ; in the case of Koch's 

 commas, the colour will have disappeared. 



Koch points out that in the bacteriological diagnosis of cholera 

 the first step is to examine the mucus in the evacuations, or in the 

 intestine if the examination is made after death. Cover-glass 

 preparations should be stained with dilute Ziehl-Neelseii solution. 

 Cultures are next made in peptone, and in eight hours will give the 

 indol reaction. In twenty-four hours the colonies may be examined 

 on plate-cultivations. The peptone cultures are prepared by adding 

 a trace of the choleraic evacuations, or of mucus containing the 

 bacilli, to a sterilised 1 per cent, solution of peptone, with *5 to 1 

 per cent, of common salt. The solution must be alkaline, and the 

 culture is placed in the incubator at 37 C. The pathogenic effects 

 can be ascertained by diffusing the bacilli from an agar- culture in 

 broth, and injecting it into the peritoneal cavity. 



Toxic Products. Brieger isolated several toxic products which he 

 had found in association with putrefaction, such as cadaverin and 

 putrescin ; but there were also present two new toxic substances, one 

 producing cramps and muscular tremors in inoculated animals, and 

 the other lowering the temperature and depressing the action of 

 the heart. Later, Brieger in conjunction with Frankel, succeeded 

 in isolating a tox-albumin from pure cultures. Guinea-pigs were 

 killed in two or three days, but rabbits had an immunity. Pfeiffer 

 found that cultures contained a poisonous principle which proved 

 fatal to guinea-pigs in extremely minute doses. It is broken up 

 by alcohol and by boiling, and secondary products formed, of very 

 much mitigated virulence. Similar toxic products were obtained 

 from cultures of both Finkler- Prior's and Metchnikoff's commas. 



Protective Inoculation. Haffkine has introduced a system of 

 protective inoculation, which is founded on the principle of inducing 

 the formation of antitoxins, or defensive proteids. Comma-bacilli 

 when first cultivated from a cholera patient are not sufficiently 



