STEREOISOMERIC LACTIC ACIDS. 233 



in saccharine media, and is on that account named Micrococcus 

 acidi paralactici. On the other hand, the aforesaid pathogenic 

 bacillus, under the same conditions, produces inactive lactic acid. 



Levo-lactic acid was first prepared in the year 1890 by FK. 

 SCHARDINGBR (II.), by means of the fermentative activity of a 

 short-rod species found in a Hungarian well-water, and to which 

 the name of Bacillus acidi Icevolactici has been given. In size 

 this organism greatly resembles Hueppe's Bacillus acidi lactici. 

 It ferments dextrose, saccharose, lactose, and glycerin, the resulting 

 products being levo-lactic acid, a little ethyl alcohol, a quantity 

 of carbon dioxide, and an unspecified combustible gas. The zinc 

 salt of inactive lactic acid is obtained by crystallisation from a 

 warmed solution of the zinc salts of this levo-lactic acid and of 

 paralactic acid. 



So far as is known at present, the Schizomycetes species forming 

 levo-lactic acid are of less frequent occurrence in nature than those 

 producing either inactive or dextro-lactic-acid. K. GUNTHER and 

 H. THIERFBLDER (I.) examined a large number of samples of sour 

 milk, in none of which could they find levo-lactic acid. Neither 

 did they succeed in isolating from the milk any fission fungus 

 capable of forming this acid, but always obtained either inactive 

 or dextro-lactic acid, or a mixture of both. This, however, does 

 not imply that Schizomycetes producing levo-lactic acid are rare. 

 On the contrary, a considerable number of species (mostly patho- 

 genic) endowed with this property are already known. Investiga- 

 tions on this point were first made by J. KUPRIANOW (I.) and 

 repeated by B. Gosio (I.), and it was shown that the amount of 

 this acid produced per unit of quantity of the fermented sugar 

 varies according to the species employed. 



Vibrio choleras asiaticce (in addition to other vibrios) was found 

 to produce levo-lactic acid, whilst Spirillum tyrogenum (Deneke) 

 produced dextro-lactic acid. On the other hand, G. LEICHMANN (I.), 

 in 1896, showed that when ordinary milk is kept at 44-5o C. 

 instead of the lower temperatures employed by Giinther and Thier- 

 f elder levo-lactic acid is invariably produced. The (long-rod) 

 fission fungus concerned in this reaction was named by LEIGH- 

 MANN (II.) Bacillus lactis acidi, a name (as we have seen in 

 135) already in use for another species of Schizomycetes as long 

 ago as 1886. 



The kind of lactic acid produced under given circumstances 

 by a certain bacterium affords, in many instances, a valuable 

 means for differentiating allied species. For example, in the 

 case of Bacillus typhi abdominalis and Bacterium coli commune, 

 the latter as shown by BLACHSTEIN (I.) produces dextro-lactic 

 acid from glucose, whilst the former, under identical conditions, 

 gives rise to levo-lactic acid. 



Nevertheless, the faculty of a given species of bacterium for 

 producing a definite kind of lactic acid must not be regarded as 



