136 PRODUCTS OF VITAL ACTIVITY. 



doubt, according to whether they are or are not supplied with atmo- 

 spheric oxygen. 



The anaerobic bacteria concerned in putrefaction have as yet re- 

 ceived comparatively little attention. Among the aerobics and fac- 

 ultative anaerobics the following are best known : Micrococcus 

 fcetidus (No. 189), Bacillus saprogenes I., II., and III., Bacillus 

 coprogenes fcetidus (No. 116), Bacillus putrificus coli (No. 324), Pro- 

 teus vulgaris (No. 97), Proteus Zenkeri (No. 100), Proteus mirabilis 

 (No. 99), Bacillus pyogenes foetidus (No. 72), Bacillus fluorescens 

 liquefaciens (No. 277), Bacillus pyocyanus (No. 95), Bacillus coli 

 communis (No. 89), Bacillus janthinus (No. 267). 



Soluble Ferments. Several species of bacteria produce soluble 

 ferments capable of changing starch into maltose, dextrin, etc. 

 Hueppe has shown that the lactic-acid bacillus produces a diastase, 

 and Miller obtained from the human intestine a species which dis- 

 solves starch. Marcano, by filtering cultures of species capable of 

 this ferment action through porcelain, was able to show that the 

 effect is due to a soluble ferment, which must have been produced 

 by the vital activity of the living microorganisms. Wortmann also 

 obtained a diastase from culture liquids which was precipitated by 

 alcohol and again dissolved in water ; in slightly acid solutions it 

 promptly converted starch into glucose. This is said to be produced 

 in culture liquids only when these do not contain albumin. In the 

 presence of albumin a peptonizing ferment was formed ; in its ab- 

 sence, a diastase by which starch was dissolved to serve as pabulum 

 for the bacteria present. These experiments were not made with 

 pure cultures, and more exact researches in this direction are de- 

 sirable. 



A peptonizing ferment for gelatin is produced by a considerable 

 number of bacteria, as stated under the heading " Liquefaction of 

 Gelatin." The jellified albumin in cultures in blood serum is also 

 liquefied by a peptonizing ferment produced by certain species of bac- 

 teria. 



Some authors also speak of a soluble ferment capable of inverting 

 cane sugar or milk sugar. According to Hueppe, such a ferment 

 is produced by the Bacillus acidi lactici. A soluble ferment for cel- 

 lulose is supposed by Fliigge to be produced by several species 

 among others by Bacillus butyricus and by Vibrio rugula. 



Several bacilli produce a soluble ferment capable of coagulating 

 the casein of milk. 



Reduction of Nitrates, and Nitrification. The researches of 

 Gayon, Dupettit, and others show that certain bacteria are able to 

 reduce nitrates with liberation of ammonia and free nitrogen. This 

 is effected in the absence of oxygen by anaerobic bacteria, and, 



