274 ACID FUCHSINE. 



added until they are neutralised and filtered, otherwise the media 

 may not be clear and transparent. This is especially so with 

 gelatin. The same amounts of acid fuchsin are added to each 

 and they are neutralised in the usual manner. 



The experiments, says the author, were made with one speci- 

 men of the Bacillus proteus vulgaris, one of the Bacillus acidi 

 lactici, one of the Bacillus lactis aerogenes, six different specimens 

 of the Bacillus typhosus, and five of the Bacillus coli co??imunis. 

 The specimens of the Bacillus typhosus and of the Bacillus coli 

 communis were obtained from different sources — from New York, 

 from the laboratory of the John Hopkins University, from the 

 laboratory of the Army Medical Museum, from the Bureau of 

 Animal Industry, and from the Hygienic Laboratory. Another 

 specimen of the Bacillus typhosus was placed at the author's dis- 

 posal through the kindness of Dr. Reed, of the Army Medical 

 Museum, and designated by him by the name of blue typhoid, on 

 account of the deep blue tint assumed by its cultures in litmus 

 milk after a certain number of days. Each experiment was 

 checked by plate cultures, so that in no instance was there 

 any contamination by other bacteria. As a general rule, the 

 cultures used in these experiments were bouillon cultures twenty- 

 four or thirty-six hours old, and at a mean temperature of 98"3°F., 

 although experiments were also made with cultures considerably 

 older and grown under different conditions. 



The following results were obtained by planting the micro- 

 organisms already mentioned in acid fuchsine bouillon : 



I. — After from six to eight hours the Bacillus acidi lactici, the 

 Bacillus coli C07?imunis, and the Bacillus lactus aerogenes, develop 

 a considerable quantity of acid, especially the Bacillus acidi lactici 

 and the Bacillus lactis aerogenes. This acid reaction is indicated 

 by the increased intensity of the pink bouillon or the appearance 

 of the pink colour in the decolourised one. 



2. — After twenty-four hours the acid reaction begins to disap- 

 pear, the bouillon has a paler tint, and, at the end of forty-eight 

 or fifty hours, they show a marked alkaline reaction, which 

 increases rapidly until the pink colour entirely disappears, the 

 cultures presenting then a yellowish hue. 



3. — The Bacillus proteus vulgaris does not present an acid 



