CHEMICAL PROCESSES IN CELLS. 147 



FERMENTATION PROCESSES, WITH TRANSFER OF OXYGEN FROM 

 THE HYDROGEN TO THE CARBON ATOMS. 



a. Lactic Acid Fermentation. — Under the action of various ferments 

 sugar is converted into lactic acid. This occurs in the milk, and also very 

 probably in sugary solutions within the intestine. In the first stage of 

 this process lactic acid is produced as follows : — 



C 6 H 12 6 = 2C 3 H 6 8 . C I2 H 22 11 +H 2 = 4C 3 H 6 O s . 



In the later stages butyric acid, carbon dioxide, and hydrogen are 

 formed. Thus : — 



3(C 3 H 6 3 ) = C 4 H 5 2 + 2C0 2 +2H 2 . 



b. Alcoholic Fermentation. — Under the influence of various of the 

 formed ferments, such as yeast-plant, grape-sugar undergoes fermentation 

 and results in the formation of carbon dioxide and alcohol. 



c. Putrefactive Fermentation. — Ferments which cause putrefaction 

 are found in the lowest organisms, micrococci, bacteria, etc. Their action 

 is destroyed by heating above 53° C. 



The most important ferments in the chemical processes occurring in 

 the animal body are the diastatic or sugar-forming ferments, found in 

 the saliva, pancreatic and intestinal juices, liver, and blood ; the peptone- 

 forming ferments, found in gastric, pancreatic, and, perhaps, intestinal 

 secretions; the fat-ferment, found in pancreatic juice; the inversive fer- 

 ment, found in intestinal juice ; and the milk-curdling ferments, found in 

 the gastric and pancreatic secretions. All the above ferments, with the 

 exception, possibly, of the last, are so-called hydrolytic ferments ; that 

 is, their action is accompanied by a process of hydration. Water is 

 essential to all forms of fermentation ; hence, ferments become inert when 

 dried. For the action of the proteolytic ferment of the gastric secretion 

 a faintly acid reaction is essential, as is also the case for the pepsin-like 

 ferment of the insectivorous plants, such as the Brosera and Dionsea, 

 which have the power of digesting albuminous bodies. An excess of 

 acid will, however, interfere with the action of the proteolytic, as well as 

 of the diastatic, ferments ; the same holds good for the caustic alkalies, 

 although an alkaline reaction favors the action of the proteolytic ferment 

 of the pancreatic juice. Salts of the heavy metals, as well as ether, 

 chloroform, and all the so-called antiseptics, prevent fermentation. 



Further details as to the action of ferments will be considered under 

 the study of the digestive juices and the putrefactive changes in the 

 alimentary canal. 



4. The Consumption and Development of Force in Cells*. — The 

 development of force in cells is closely dependent on the chemical inter- 



* Wundt, " Lehrbuch der Physiol ogie." 



