276 AC^D FUCHSINE. 



2. — At the end of forty-eight or fifty hours the Bacillus colt 

 communis and the Bacillus pro teus vulgaris also produced an acid, 

 so that the cultures became quite red. 



3. — The Bacillus typhosus does not show any marked acid 

 production until the fifth or seventh day, when it acquires the 

 same tint as the others. 



By observing the colour of the cultures, says Dr. Penny, after 

 forty-eight or fifty hours, it is very easy to distinguish the pale pink 

 or colourless culture of the Bacillus typhosus from the intensely 

 red of the other organisms. As these results have been constant 

 and have not shown any variation in a very long series of experi- 

 ments made under different circumstances, this test is positive, 

 establishing the presence of or distinguishing the Bacillus typhosus 

 from the other intestinal micro-organisms, and especially from the 

 Bacillus coli cofjununis. 



It v^rill be noticed that the change of reaction brought about in 

 the glycerin peptone solution with acid fuchsine is different from 

 what takes place in the bouillon, for while the last stage in the 

 bouillon cultures is one of alkalinity after a period of acidity 

 (except in the case of the Bacillus proteus vulgaris^ which has no 

 initial acid stage), in Dunham's solution with glycerin and acid 

 fuchsine no marked change is observed at the beginning, and the 

 last stage is one of acidity. In this case the change of reaction 

 is produced in all probability by an oxygenation of the glycerin ; 

 while in the case of bouillon the reaction is due to the influence 

 of the germs on the inosite or any other hydrocarbonates. 



Beautiful results were also observed by planting the Bacillus 

 coli commu?iis and the Bacillus typhosus in Dunham's solution with 

 glycerin and fuchsine, to which agar agar or gelatin has been 

 added. Stab cultures of the Bacillus coli commujiis and the 

 Bacillus typhosus, made in the agar medium and kept at 98-3^ R, 

 showed the following results : Those of the Bacillus coli communis 

 were pinker than those of the Bacillus typhosus^ the pink colour 

 being more marked along the stab, although it was diffused 

 throughout the agar. The pink colouration increased, and on the 

 third day the culture presented a brilliant red colour. On the 

 other hand, the cultures of the Bacillus typhosus showed at the 

 end of forty-eight hours a pink tint at the upper part of the stab. 



