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TEXT-BOOK OF PHYSIOLOGY. 



any marked difference between the resting and active conditions. According 

 to some observers they contain pepsinogen; according to others, mucin. 

 The epithelial cells lining the ducts of the pylorus and fundus glands, if not 

 identical with the epithelial cells on the surface of the mucous membrane, 

 pass by transitional forms into them. Among these cells are found many 

 goblet cells which secrete a portion of the mucin found in the stomach and 

 gastric juice. In the period of rest the protoplasm of the epithelial cells 

 absorbs and assimilates from the surrounding lymph-spaces material which 

 eventually makes its reappearance as a product of metabolism in the form of 

 granules and hydrochloric acid. With the onset of digestive activity there 

 is a dilatation of the blood-vessels, an increase in the blood-supply, a stimu- 

 lation through the nerve-supply of the cells, and an output of a fluid to which 

 the name gastric juice is given. 



_...& 



A ' B 



FIG. 76. SECRETIONS OF DEEP ENDS OF FUNDUS GLANDS OF THE CAT IN DIFFERENT SECRE- 

 TIVE PHASES. X 1000. (Bensley). A . From a fasting stomach. The chief cells are filled with 

 large zymogen granules; nuclei near the outer ends of cells. Gentian- violet preparation. 

 b b b. Border cells. B. Six hours after an abundant meal of raw flesh. The chief cells exhibit 

 two zones, the inner occupied by large zymogen granules, the outer by a deeply staining, obscurely 

 fibrillar element, prozymogen; the nuclei lie at the junction of the two zones, b b b. Border 

 cells, pr. Prozymogen. c. Mucin-secreting cells, similar to those found hi the neck of the gland. 

 Gentian- violet preparation. (Hemmeter after Bensley.} 



The Physiologic Action of Gastric Juice. In the study of the physi- 

 ology of gastric digestion as it takes place under normal conditions it is 

 important to bear in mind that the foods introduced into the stomach are 

 heterogeneous compounds consisting of both nutritive and non-nutritive 

 materials, and that before the former can be digested and utilized for nutri- 

 tive purposes they must be freed from their combinations with the latter. 

 This is accomplished by the solvent action of the gastric juice, which in 

 virtue of the chemic activity of its constituents on proteins, gradually disinte- 

 grates the food and reduces it to the liquid or semiliquid condition. 



The nature of this change and the respective influence which the acid 

 and pepsin exert can be studied with almost any form of protein. A most 

 convenient form, however, is fibrin obtained from blood by whipping and 

 thoroughly freed from corpuscles by washing under a stream of water. The 

 chemic features of proteins, as well as the typical forms contained in the 



