FERMENTATION OF THE PROTEIDS. 375 



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

 for fermentation. Calcium formiate mixed with cloacal-mucus fer- 

 ments 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, we are acquainted with the fermentations of 

 lactic, glycerinic, malic, tartaric, and citric acids. 







1 2 



Fig. 148. 



Bacillus subtilis 1, spore ; 2, 3, 4, germination of the spores ; 5, 6, short rods ; 

 7, jointed thread, with the formation of spores in each segment or cell; 8, 

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

 10, fungus with a cilium. 



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

 and acetic acids, C0 2 H 2 O. Other ferments cause the formation of valerianic 

 acid. Glycerinic acid, in addition to alcohol and succinic, yields chiefly acetic acid; 

 malic acid forms succinic and acetic acid. The other acids above enumerated 

 yield somewhat similar products. 



III. Fermentation of the Proteids. There do not seem to be 

 fungi of sufficient activity in the intestine to act upon undigested 

 proteids and their derivatives. Many schizomycetes, however, can pro- 

 duce a peptonising ferment. 



We have already seen that pancreatic digestion (p. 341), acts upon 

 the proteids, forming, among other products, amido-acids, leucin, tyrosin, 

 and other bodies. Under normal conditions, this is the greatest decom- 

 position produced by the pancreatic juice. The putrefactive fermentation 

 of the large intestine (Hiiffner, Nencki) causes further and more profound 

 decompositions. Leucin (C 6 H 13 N0 2 ) takes up two molecules of water 

 and yields valerianic acid (C 5 H 10 O 2 ), ammonia, CO 2 and 2(H 2 ); 

 glycin behaves in a similar manner. Tyrosin (C 9 H U N0 3 ) is decom- 

 posed into indol (C 8 H 7 N), which is constantly present in the intes- 

 tine (Kuhne), C0 2 H 2 ON (Nencki). If be present, other decom- 

 positions take place. These putrefactive products are absent from 

 the intestinal canal of the foetus and the newly-born (Senator). 

 During the putrefactive decomposition of proteids, C0 2 H 2 S, also H 

 and CH 4 , are formed; the same result is obtained by boiling them with 



