CHAP. X.] LACTIC AND BUTYRIC FERMENTATIONS IN INTESTINES. 437 



As we shall have occasion to point out in the next chapter, when 

 considering the processes which have their seat in the small intestine 

 as a whole, so great is the quantity of organic acids formed by the 

 organised ferments of the small intestine that in spite of the sodium 

 carbonate which the mucous membrane is, doubtless, perpetually 



secreting during digestion, the contents of the small intestine from 

 pylorus to csecum are, in opposition to the hackneyed teaching of 

 the schools, always acid. 



fMany researches have, of recent years, been conducted on the 

 micro-organisms of the small intestine and on the fermentations to 

 which they give rise, and of these the most important is that con- 

 ducted by Nencki, Macfadyen and Sieber, the mean results of which 

 have been summarised by the Author in the accompanying table, to 

 which the reader is referred. It will be seen that these investigators 

 were able to identify seven individual micro-organisms which give 

 rise to fermentations in the small intestines. Of these only two 

 excited any action on the albuminous substances (Streptococcus 

 liquefaciens ilei and Bacillus liquefaciens ilei). With the exception 

 of the last-named, all the six others exert a powerful action on 

 dextrose. Five of the seven decompose dextrose with the production 

 of alcohol, often in large quantities; six of the seven produce lactic 

 acid. Amongst them, the most active is the Streptococcus liquefaciens 

 ilei, which when acting on a solution of dextrose, converts nearly the 

 whole of the sugar into inactive lactic acid (ordinary lactic acid of 

 fermentation, optically inactive ethylidene-lactic acid 1 ). 



The conversion of dextrose into lactic acid under the influence of 

 ferments is a process of simple decomposition which is identical with 

 that which occurs when it is heated with caustic alkalies, and it 

 may be represented by the following equation: 



C 6 H 12 6 = 2 (CH 3 - CH . OH - COOH). 



The conversion of dextrose into alcohol, if we leave out of 

 consideration the very numerous by-products which are formed in 

 the process and confine our attention merely to the two principal 

 products formed (alcohol and C0 2 ), may be represented by the 

 following equation : 



C 6 H 12 6 = 2 (C 2 H 5 . OH) + 2C0 2 . 



Although Nencki's researches do not give any facts bearing on 

 the question, it is probable enough that the butyric acid fermentation 

 occurs in the intestine. Under the influence of certain of the 

 ferments, particularly of the Bacterium ilei (Frey), the products 

 of fermentation separated were succinic acid, sarcolactic acid and 

 alcohol, large quantities of a mixture of C0 2 and H being evolved. 



1 See Vol. i. (1st edit.), p. 362. 





