THE DIGESTIVE SECRETIONS 921 



alkaline medium. Curiously enough, therefore, we are confronted here 

 by the peculiar functional arrangement that the alkaline product of the 

 chief cells is acidified almost immediately by the secretion of the parietal 

 cells, and that the alkaline" juice of the pyloric part of the stomach 

 must first be mixed with the f undic acid before it can exert its charac- 

 teristic action. 



The genesis of hydrochloric acid has also received attention from 

 the chemists. Thus, it has been suggested that it is derived from the 

 chlorids of the blood, but the nature of this decomposition is not known. 

 The contrary view is that it orginates from the sodium chlorid of the 

 food upon the surface of the gastric mucosa. The latter view, however, 

 could be criticized upon the ground that a copious secretion of gastric 

 juice containing an abundant quantity of hydrochloric acid, may also 

 be evoked without the introduction of food into the stomach ; for ex- 

 ample, by the process of sham-feeding, or by allowing an animal to see 

 or to smell food. More recently, the preceding hypothesis pertaining 

 to the origin of the hydrochloric acid in the parietal cells has received 

 additional support in the results of the microchemical tests of Fitz- 

 gerald ^ and Hammett.2 On injecting a ferrocyanid and a ferric 

 salt into the circulation of animals, a deposition of Prussian blue was 

 noted not only in the lumina of the gastric glands bu : also in the cannal- 

 iculi of the parietal cells and even within the cytoplasm of the latter. 

 Since this characteristic precipitate was not found in the chief cells 

 and results only in the presence" of free acid, it was concluded that the 

 hydrochloric acid orginates in the border cells. Harvey and Bensley^ 

 are at issue with this view, because they state that the parietal cells are 

 alkaline in their reaction and believe that a deposition of this coloring 

 material takes place only upon the mucosa of the stomach and in the 

 orifices of the ducts of the different glands. Without entering in 

 detail into the technique of the microchemical tests of Hammett, it 

 may be stated that these later experiments fully confirm the conten- 

 tion of Heidenhain that the parietal cells secrete the hydrochloric acid. 



The gastric glands, therefore, present the same functional picture 

 as the salivary glands. They are not merely passive filters but living 

 laboratories in which the contents of the blood and lymph are drawn 

 upon to yield new and very characteristic vital products. This can 

 easily be proven by comparing the composition of the gastric secre- 

 tion with that of the body-fluids. Thus, we obtain in the former such 

 characteristic bodies as mucin, pepsin, hydrochloric acid, and rennin. 



Methods Employed to Obtain Gastric Juice. — The experiments of 

 the older observers (Spallanzani, 1729-1799) were carried out with 

 various foods which were sewed in linen bags or enclosed in perforated 

 capsules of wood. Clean sponges attached to strings have also been 

 used, the sponges being removed later on and their contents squeezed 



1 Proc. R. Soc, London, 1910. 



2 Anat. Record, ix, 1915, 21. 



3 Biolog. Bull., xxiii, 1912, 225. 



