SECRETION. ' 179 



described for other gland-cells (p. 167), this appearance is possibly connected 

 with the formation of the secretion. 



The duct of a gastric gland was formerly supposed to be a simple tube 

 extending the length of the gland. A number of recent observers, Jjowever, 

 have shown, by the use of the Golgi stain, that this 

 view is not entirely correct, at least not for the glands 

 in the fundus in which border-cells are present. In 

 these glands the central lumen sends offside channels 

 which pass to the border-cells and there form a net- 

 work of small capillaries which lie either in or round 

 the cell. 1 An illustration of the duct-system of a 

 fundic gland is given in Figure 79. If this \vork 

 is correct it would seem that the chief-cells com- 

 municate directly with the central lumen, but that FIG. 79. Ducts and secretion 

 the border-cells have a svstem of secretion canillirips capillaries to parietal cells. 



Gland from the fundus of cat's 



of their own, resembling in this respect the demi- stomach (after Langendorff 

 Junes of the mucous salivary glands (p. 161). This 



fact tends to corroborate the statement previously made, that the border-cells 

 form a distinct type of cell whose function is probably different from that 

 of the chief-cells. 



Composition of the Secretion of the Gastric Mucous Membrane. 

 The secretion as it is poured out on the surface of the mucous membrane is 

 composed of the true secretion of the gastric glands together with more or less 

 mucus, which is added by the columnar cells lining the surface of the mem- 

 brane and the mouths of the glands. In addition to the mucus, water, and 

 inorganic salts, the secretion contains as its characteristic constituents hydro- 

 chloric acid and two enzymes namely, pepsin which acts upon proteids, and 

 rennin which has a specific coagulating effect upon the casein of milk. For an 

 analysis of the gastric secretion of the dog see p. 161. According to Heiden- 

 hain, 2 the secretion from the pyloric end of the stomach is characterized by the 

 absence of hydrochloric acid, although it still contains pepsin. This statement 

 rests upon careful experiments in which the pyloric end was entirely resected 

 and made into a blind pouch which was then sutured to the abdominal wall 

 to form a fistula. In this way the secretion of the pyloric end could be obtained 

 free from mixture with the secretion of any other part of the alimentary canal. 

 By this means Heideuhain found that the pyloric secretion is an alkaline liquid 

 containing pepsin. This fact forms the strongest evidence for Heidenhain's 

 hypothesis that the HC1 of the normal gastric secretion is produced by the 

 "border-cells" of the fundic glands and the pepsin by the "chief-cells," since 

 HC1 is formed only in parts of the stomach containing border-cells, whereas 

 the pepsin is produced in the pyloric end, where only chief-cells are present. 



Evidence of this character is naturally not very convincing, and the hypoth- 



1 Langendorff and Laserstein : Pfluger's Archiv fur die gesammte Physiologic, 1894, Bd. Iv. S. 

 578. 



2 Archiv jiir die gesammte Physiologic, 1878, Bd. xviii. S. 169, also Bd. xix. 



