328 FORMATION OF HYDROCHLORIC ACID. 



The animals experimented on died, at the latest, after six days. The secretion of 

 this part was thin, alkaline, and contained 2 p.c. of solids, including pepsin. 



In the frog, the alkaline glands of the oesophagus contain only 

 chief cells which produce pepsin; while the stomach has glands which 

 secrete acid (and perhaps some pepsin), and are lined by parietal 

 cells (Partsch, v. Swiecicki). Amongst fishes, the carps have no fundus- 

 glands in the stomach (Luchau). 



[The secreting portions of glands of the cardiac sac (crop) of the herring, are 

 lined by a single layer of polygonal cells (VV. Stirling).] 



The hydrochloric acid is formed, according to Heidenhain, by the 

 parietal cells. It occurs on the free surface of the gastric mucous mem- 

 brane as well as in the ducts of the gastric glands. The deep parts of 

 the glands are usually alkaline. Free HC1 is detected in human gastric 

 juice, within 45 minutes to 1-2 hours after a moderate meal (von den 

 Velden, and others), and 3-4 hours after a full meal (Edinger); the 

 amount gradually increases during the process of digestion (Kretschy 

 and Uffelmann). 



Cl. Bernard injected potassium ferrocyanide and afterwards lactate of iron into 

 the veins of a dog. After death, blue colouration occurred only in the upper, acid 

 layers of the mucous membrane. Nevertheless we must assume, that the hydrochloric 

 acid is secreted in the parietal cells of the fundus of the glands, and that it is 

 rapidly carried to the surface along with the pepsin. 



Briicke neutralised the surface of the gastric mucous membrane with magnesia 

 usta, chopped up the mucous membrane with water and left it for some time, when 

 the fluid had again an acid reaction. 



With regard to the formation of a free acid, the following statements 

 may be noted : The parietal cells form the hydrochloric acid from the 

 chlorides which the mucous membrane takes up from the blood. Accord- 

 ing to Voit, the formation of acid ceases if chlorides be withheld from the 

 food. The active agent is lactic acid, which splits up sodium chloride 

 and forms free HC1 (Maly). The base set free is excreted by the urine, 

 rendering it at the same time less acid (Jones, Maly). The formation 

 of acid is arrested during hunger. According to H. Schulz, watery 

 solutions of alkaline and earthy chlorides are decomposed, even at a low 

 temperature, by C0 2 , free hydrochloric acid being formed. 



[A solution of sulphate of soda, not sufficiently strong to cause inflammatory 

 redness of the gastric mucous membrane, yet concentrated enough to excite 

 secretion, causes, when injected into the empty stomach, the pouring out of an 

 alkaline, not an acid secretion (Matthew Hay).] 



Secretion. When the stomach is empty, there is no secretion of 

 gastric juice ; this occurs only after appropriate (mechanical, thermal, 

 or chemical) stimulation. In the normal condition, it takes place imme- 

 (Jiately pn the introduction of food, but also of indigestible substances, 



