332 BACTERIAL FERMENTATION IN THE INTESTINES. 



Aldehyd is changed by oxidation into acetic acid (C 2 H 4 O 2 ). Accord- 

 ing to Nageli, the same micro-organism is capable of producing small 

 amounts of carbon dioxid and water. As acetic fermentation ceases at 

 35 C., it will not take place in the intestine, so that the acetic acid con- 

 stantly met with in the feces must result from other fermentative pro- 

 cesses. Thus, it is produced in considerable amount in herbivora as a 

 product of the fermentation of cellulose; being, after absorption, burned 

 up in the fluids of the body. Acetic acid is formed also as a result 

 of the putrefaction of albuminates with exclusion of air. 



5. Also partial solution of starch and of cellulose is caused by schizo- 

 mycetes (bacillus butyricus, bacterium termo, vibrio rugula) in the 

 intestines; for cellulose, mixed with cloacal discharge or the intes- 

 tinal contents, is transformed into a sugar-like carbohydrate, which 

 then breaks up into equal volumes of carbon dioxid and marsh-gas. 

 The neurin produced by the pancreas also yields marsh-gas (CH 4 ), in 

 addition to carbon dioxid. 



The solution of the cellulose of the cell-walls then permits the action 

 of the digestive juices upon the enclosed digestible portions of the 



n 



34 



FIG. 123. Hay-bacillus (Bacillus subtilis): i, spore; 2, 3, 4, germination of the spore; 5, 6, short bacilli; 7, 

 jointed filament with spore-formation in each cell; 8, short bacilli, in part with spore-formation; 9, spores in 

 individual short bacilli; 10, bacteria with flagella. 



vegetable food. In human beings the metabolism of cellulose is always 

 slight, while in herbivora it is digested in considerable amounts. 



6. Bacillus subtilis, cheese-spirilli and others are capable of trans- 

 forming starch into sugar. 



7. Micro-organisms (lactic-acid bacilli?) that produce invertin also 

 occur in the intestinal canal. This substance can be obtained also from 

 brewer's yeast by agitation with water and ether and subsequent fil- 

 tration. 



Fermentation of Fats. Putrefaction is capable, with the aid of as 

 yet unknown micro-organisms, of decomposing neutral fats into glycerin 

 and fatty acids, after taking up water. Glycerin is susceptible of varied 

 fermentations with different microbes, as, for example, the bacillus 

 Fitzianus. When the reaction is neutral, hydrogen and carbon dioxid 

 are formed, together with succinic acid and a mixture of fatty acids. 



Fitz observed alcohol, together with caproic, butyric and acetic acids, develop 

 as a result of the action of the hay-bacillus (bacillus subtilis, Fig. 123), while in 

 other cases butyl-alcohol principally resulted, van de Velde found butyric and 

 lactic acids, together with traces of succinic acid, and also carbon dioxid, water 

 and nitrogen. 



