374 FERMENTATION OF THE FATS. 



The fungi which occur everywhere in the atmosphere are the cause of the spon- 

 taneous acidification, and subsequent coagulation of milk. See Milk. 



(2.) Bacillus butyricus (B. amylobacter, Van Tieghem ; Clostridium 

 butyricum, Vibrion butyrique, Pasteur), which in the presence of starch 

 is often coloured blue by iodine, changes lactic acid into butyric acid, 

 together with CO 2 and H (Prazmowski). 



C C 4 H 8 O 3 =1 butyric acid. 



2 (C 3 H 6 3 ) lactic acid= -! 2 (C0 2 ) = 2 carbonic acid. 

 v 4 H = 4 hydrogen. 



This fungus (Fig. 147, B) is a true anaerobe, and grows only in the absence of O. 

 The lactic acid fungus uses O very largely, and is, therefore, its natural precursor. 

 The butyric acid fermentation is the last change undergone by many carbo- 

 hydrates, especially of starch and inulin. It takes place constantly in the faeces. 



(3.) A fungus, whose nature is not yet determined, causes alcohol to 

 be formed from carbohydrates (Fitz). 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 (p. 298, I). 



(4.) Bacterium aceti (Fig. 147, A) converts alcohol into acetic acid outside the 

 body. Alcohol (C 2 H 6 0) + = C 2 H 4 O ( Aldehyd) + H 2 O. Acetic acid (C 2 H 4 O 2 ) 

 is formed from aldehyd by oxidation. According to Nageli, the same fungus causes 

 the formation of a small amount of C0 2 and H 2 0. As the acetic fermentation is 

 arrested at 35C., this fermentation cannot occur in the intestine, and the acetic 

 acid, which is constantly found in the faeces, 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 of 

 the intestine. If cellulose be mixed with cloacal-mucus (Hoppe- 

 Seyler), or with the contents of the intestine (Tappeiner), n molecules, 

 [n (C 6 H 10 5 )], take up n molecules of water, +w(H 2 0), and produce 

 three times n molecules C0 2 , and three times n molecules of marsh- 

 gas 3 n (CH 4 ). 



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

 (1 and cellulose) into sugar, others excrete invertin e.g., the Leuko- 

 nostoc mesenteriodes, which develops in the juice of turnips. Invertin 

 changes cane-sugar into invert-sugar ( 183, II, 5). 



II. Fermentation of the Pats. In certain putrefactive conditions, 

 organisms of an unknown nature can cause neutral fats to take 

 up water and split into glycerine and fatty acids. Glycerine C 3 H 5 

 (H0) 3 is a triatomic alcohol, and is capable of undergoing several 

 fermentations, according to the fungus which acts upon it. With a 

 neutral reaction, in addition to succinic acid, a number of fatty acids, 

 H and C0 2 , are formed. 



Fitz found under the influence of the hay-fungus (Bacillus subtilis, Fig. 148) 

 alcohol with caproic, butyric, and acetic acids ; in other cases butylic alcohol is 

 the chief product. 



