234 OPTICALLY ACTIVE FERMENTATION PRODUCTS. 



unconditional. On the contrary, a good deal depends on the con- 

 ditions of nutrition. The necessity for the maintenance of iden- 

 tical conditions during experiments of this kind has already been 

 emphasised, and it should be also mentioned that the results are 

 influenced not only by the kind of carbohydrate (sugar) subjected 

 to fermentation, but also by the constitution of the nitrogenous 

 nutrient material. For this discovery we are indebted to A. PERE 

 (I.), who showed that when ammonia salts alone (unaccompanied 

 by peptone) are at the disposal of the microbe, both B. typhi 

 abdominalis and Bacterium coli commune produce levo-rotatory 

 lactic acid from glucose. 



The separation of optically active compounds by means of 

 Eumycetes will be frequently referred to in the second volume, so 

 we will only mention a treatise by M. VON NENCKI (II.), which 

 describes a valuable method for manipulating fermenting liquids 

 and determining their content of optically active lactic acid. The 

 characteristics of the salts of this acid have been described by T. 

 PURDIE and J. WALLACE WALKER (II.). According to F. HOPPE- 

 SEYLER and FR. ARAKI (I.), the lithium salts are the most suit- 

 able compounds to employ in experiments for determining the 

 rotatory power of the various lactic acids. 



