158 MANUAL OF PHYSIOLOGY. 



not give an acid reaction, while the neck and orifices of the gland 

 are distinctly acid, there is good reason for believing that this 

 manufacture of acid from the alkaline blood is really an active 

 process carried out by some glandular cells. 



It has been suggested that the cell elements which produce the 

 acid are the ovoid border cells, from whence it rapidly passes to 

 the orifice of the glands. This view is supported by the alka- 

 linity of the pyloric end of the stomach where the border cells 

 are not found. In some animals the distinct distribution of the 

 diiferent cell elements and the accompanying reaction of the 

 secretion are well marked. 



ACTION OF THE GASTRIC JUICE. 



The gastric juice has, in the absence of mucus, no effect on the 

 carbohydrates, and probably the amylolytic fermentation set up 

 by the saliva is impeded, if not completely checked, by the free 

 acid in the stomach. 



The gastric juice has no effect on pure fats, but it dissolves the 

 proteid framework of adipose tissue and thus sets the fats free, 

 which are then turned by heat to a liquid mass like oil. Upon 

 the albuminous bodies the gastric digestion produces a marked 

 effect. The proteids being colloid bodies cannot pass through an 

 animal membrane by the process called dialysis ; it has, therefore, 

 been assumed that they cannot be absorbed through the lining 

 membrane of the stomach. They are, also, often eaten in an insol- 

 uble form. To convert the insoluble and indiffusible albumins 

 into a soluble and diffusible substance would obviously be a great 

 step toward their absorption. This power is ascribed to the gas- 

 tric juice. The steps of the process may be accurately followed 

 in a suitable glass vessel, irrespective of the stomach, by using 

 artificial gastric juice, and attending to the various conditions 

 necessary for its action. The power of artificial gastric juice 

 carefully prepared from the mucous membrane of an animal's 

 stomach differs in no essential respect from that of the natural 

 secretion in the stomach, if all the circumstances which aid the 

 action of the gastric ferments be applied in the experiment. This 

 action consists in a conversion of coagulated albumins into the 



