BACTERIAL FERMENTATION IN THE INTESTINES. 333 



The fatty acids yield, chiefly as calcium-soaps, material suitable for 

 fermentation. Calcium formate, in fermentation with cloacal discharge, 

 yields calcium carbonate, carbon dioxid and hydrogen; calcium acetate 

 yields calcium carbonate, carbon dioxid and marsh-gas. Of the oxy- 

 acids, the fermentation of lactic, gly eerie, malic, tartaric and citric acids 

 is known. 



According to Fitz, lactic acid, in combination with calcium, yields propionic 

 acid, acetic acid, carbon dioxid and water. Valerianic acid in considerable 

 amount is produced by other excitants of fermentation. Glyceric acid yields 

 especially acetic acid, in addition to alcohol and succinic acid. Malic acid forms 

 succinic acid and some acetic acid; as a result of other fermentative processes, 

 propionic acid, and of still other fermentative processes, butyric acid, together 

 with hydrogen; or it is decomposed into lactic acid and carbon dioxid. Tartaric 

 acid breaks up into acetic acid, propionic acid, carbon dioxid and water; as a 

 result of the action of other microbes, into butyric acid; and of that of still others, 

 into acetic acid, together with some butyric and succinic acids and alcohol. Citric 

 acid yields finally acetic, with some butyric and succinic acids. 



Fermentations of Proteids. In the fermentation of the undigested 

 proteids in the intestine and their derivatives, which takes place princi- 

 pally in the large intestine, micro-organisms likewise appear to take part. 

 In the first place it should be emphasized that some schizomycetes are 

 capable of producing peptonizing ferment, as, for example, the bacillus 

 subtilis, bacillus liquefaciens ilei, the cheese-spirilli, the micro-organisms 

 of pickled herring, etc., so that assistance to the peptic enzyme, even 

 though slight, on the part of these microbes appears to be not wholly ex- 

 cluded. 



It has been found that pancreatic digestion of albuminates does not 

 proceed beyond the production of amido-acids : leucin, tyrosin and others. 

 Putrefactive fermentation in the large intestine causes still further and 

 more profound decompositions. Leucin (C 6 H 13 NO 2 ), by taking up two 

 molecules of water, forms valerianic acid (C 5 H 10 O 2 ), ammonia, carbon 

 dioxid and four molecules of hydrogen. Glycin behaves in a similar 

 manner. Tyrosin (CgHuNC^) breaks up into indol (C 8 H 7 N), which is 

 constantly encountered in the intestine, together with carbon dioxid, 

 water and hydrogen. If the admission of oxygen is possible, still other 

 decompositions take place. These products of putrefaction are wanting 

 in the intestine of the fetus and the new-born. In the putrefactive de- 

 compositions of proteids, as well as upon boiling them with alkalies, 

 carbon dioxid and hydrogen sulphid develop, together with hydrogen 

 and marsh-gas. Under such circumstances, gelatin yields, in addition 

 to abundant leucin, much ammonia, carbon dioxid, acetic, butyric and 

 valerianic acids and glycin. Mucin and nuclein undergo no decomposi- 

 tion. Artificial digestive experiments with the pancreas disclose an 

 extraordinary tendency to putrefactive decomposition. 



The body giving rise to the fecal odor, which likewise results from putre- 

 faction, has not as yet been discovered. It is intimately related to indol and 

 skatol, but these are odorless when prepared in the pure state. 



Among the solid matters in the large intestine produced only by 

 putrefaction, indol (C 8 H 7 N) is especially to be pointed out. 

 substance that results also from heating albuminates with alkalies, or 

 in small amount by superheating them with water to 200 C. 

 forerunner of indican in the urine. If the products of the digestion of 

 albuminates, the peptones, are rapidly absorbed in the intestine, only a 



