CHEMISTRY OF THE DIGESTIVE PEOCESSES. 



BY B. MOORE. 



CONTENTS : Digestive Ferments, p. 312 Chemical Composition of Digestive Juices, 

 p. 342 Saliva, p. 342 Gastric Juice, p. 349 Pancreatic Juice, p. 366 Intes- 

 tinal Juice, p. 368 Bile, p. 369 Digestion of Carbohydrates, p. 392 Digestion 

 of Proteids, p. 428 Absorption of Carbohydrates and Proteids, p. 430 

 Digestion and Absorption of Fats, p. 443 Bacterial Digestion, p. 463 Com- 

 position of Fa3ces, p. 472. 



THE DIGESTIVE FERMENTS, OR ENZYMES. 



Organised and unorganised ferments. Fermentation is invariably 

 brought about, directly or indirectly, by cell life, either vegetable or 

 animal. When the action is direct, and the chemical changes involved 

 in the process occur only in the presence of the cell, the latter is 

 spoken of as an organised ferment. When the action is indirect, and 

 the changes are the result of the presence of a soluble material secreted 

 by the cell acting apart from the cell, this soluble substance is termed 

 an unorganised ferment, soluble ferment, or enzyme. 1 



The action of an organised ferment is intimately connected with the 

 life of the cell, and is instantly stopped by anything which either kills 

 the cell or temporarily arrests its activity; while that of a soluble 

 ferment is not a vital process, but one which is purely physical or 

 chemical in its nature. As a consequence, an organised ferment is 

 destroyed, and its specific action stopped, by any protoplasmic poison, 2 

 while an unorganised ferment, provided it is not precipitated, is un- 

 affected by such reagents. 



All the differences in the mode of action of organised and un- 

 organised ferments arise from this close connection of the organised 

 ferment with the cell. Thus, an organised ferment, provided there is a 

 supply of nitrogenous food at its disposal, can grow and multiply in a 

 medium in which it is sown, while an unorganised ferment can never so 

 increase in quantity ; from this it follows that the rapidity of action of 

 an unorganised ferment depends (within limits) on the initial quantity 

 added, but in the case of an organised ferment the initial amount soon 

 becomes a matter of no moment. 



Organised ferments are unicellular organisms (microfungi), while the 



1 This term was first used by Kiihne, Verhandl. d. naturJi.-med. Ver. zu Heidelberg, 

 1879, N. F., Bd. i. S. 236. 



2 Such as any of those substances commonly known as antiseptics. 



