FEKMENTATION OF PROTEIDS. 



28l 





This fungus (fig. 203, B) is a true anaerobe, and grows only in the absence of 0. The lactic acid 

 fungus uses very largely, and is, therefore, its natural precursor. The butyric acid fermenta- 

 tion is the last change undergone by many carbohydrates, especially by starch and inulin. It 

 takes place constantly in the feces. 



(3) Certain micrococci cause alcohol to be formed from carbohydrates. The 

 presence of yeast may cause the formation of alcohol in the intestine, and in both 

 cases also from milk-sugar, which first becomes changed into dextrose. 



(4) Bacterium aceti (fig. 203, A) converts alcohol into acetic acid outside the body. Alcohol 

 (C 2 H 6 0) + - C 2 H 4 ( Aldehyd) + H 2 0. Acetic acid (C 2 H 4 2 ) is formed from aldehyd by oxida- 

 tion. According to Nageli, "the same fungus causes the formationlof a small amount of C0 2 and 

 H 2 0. As the acetic fermentation is arrested at 35 C, this fermentation cannot occur in the 

 intestine, and the acetic acid, which is constantly found in the feces, must be derived from 

 another source. During putrefaction of the proteids, with exclusion of air, acetic acid is 

 produced (Nencki). 



(5) Starch, and cellulose are partly dissolved by the schizomycetes (Bac. butyricus 

 and Vibrio rugula) of the intestine. If cellulose be mixed with cloacal-mucus, 

 or with the contents of the intestine, it passes into a saccharine carbohydrate which 

 decomposes into equal volumes of C0 2 and CH 4 (Hoppe-Seyler). 



(6) Fungi, whose nature is unknown, can partly transform starch and 

 cellulose) into sugar. 



(7) Others produce invertin. Invertin changes cane-sugar into invert-sugar 

 ( 183, II., 5). Cane-sugar, C 12 H 22 C n + H 2 = C 6 H 12 6 (Dextrose) +C 6 H 12 6 

 (Lsevulose). 



II. Fermentation of Fats ( 251). During putrefaction, organisms of an 

 unknown nature cause neutral fats to take up water and split into glycerine and 

 their corresponding 

 fatty acid ( 170). 

 Qlycerine is cap- 

 able of undergoing Q 

 several fermenta- 

 tions, according to Jf 

 the fungus which 

 acts upon it (251). 

 With a neutral re- 

 action, in addition 



to succinic acid, a Fi 204. 



number of fatty Baci u us su UMs. 1, spore ; 2, 3, 4, its germination ; 5, 6, short rods ; 

 acids, H and C0 2 , 7, jointed thread, with the formation of spores in each segment ; 8, 

 are formed. short rods, some of them containing spores ; 9, spores in single short 



Fitz found that the rods > 10 fun g us with a cilium 

 hay-bacillus (Bacillus subtilis, fig. 204) formed alcohol with caproic, butyric, and acetic acids ; 

 in other cases, especially butylic alcohol, van de Velde found butyric, lactic, and traces of suc- 

 cinic acid with C0 2 , H 2 0, N. 



The fatty acids, especially as chalk soaps, form an excellent material for 

 fermentation. Calcium formiate mixed with cloacal-mucus ferments and yields 

 calcium carbonate, C0 2 and H ; calcium acetate, under the same conditions, 

 produces calcium carbonate, C0 2 and CH 4 . Amongst the oxy-acids y we are 

 acquainted with the fermentations of lactic, glycerinic, malic, tartaric, and citric 

 acids. 



According to Fitz, lactic acid (in combination with chalk) produces propionic and acetic 

 acids, C0 2 , H 2 0. Other ferments cause the formation of valerianic acid. Glycerinic acid, in 

 addition to alcohol and succinic acid, yields chiefly acetic acid ; malic acid forms succinic and 

 acetic acid. The other acids above enumerated yield somewhat similar products. 



III. Fermentation of Proteids ( 249). The undigested proteids and their 

 derivatives appear to be acted upon by fungi. Many schizomycetes (hay bacillus 

 and Bac. subtilis), however, can produce a peptonising ferment. We have already 





 2 



? 

 3 



v 



