FORMATION OF HYDROCHLORIC ACID. 



245 



dilute hydrochloric acid, or with this acid and glycerine. The relative amount of pepsinogen 

 and pepsin in a fluid may be determined approximately by the method of Langley and Edkins. 

 A 1 per cent, solution of sodic carbonate exerts a greater destructive action on pepsin than on 

 pepsinogen, while a current of C0 2 destroys pepsinogen to a greater extent than pepsin. Both 

 substances are unaffected by CO, but are destroyed at 54 to 57 C] 



The pyloric glands secrete pepsin, but no acid. Klemensiewicz excised in a 

 living dog the pyloric portion of the stomach, and afterwards stitched together the 

 duodenum and the remaining part of the stomach. The excised pyloric part, with 

 its vessels intact, he stitched to the abdominal wall, after sewing its lower end. 

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

 this part was thin, alkaline, and contained 2 per cent, of solids, including pepsin. 



[Pyloric Fistula. In fig. 185 P represents the excised pyloric portion, C the cardiac. The 

 parts a, a, and a' a' were then stitched together, and the con- 

 tinuity of the organ established. The lower end (d) of P was 

 closed by sutures, while the edges of P at were stitched to 

 the abdominal walls, thus making a pyloric fistula. ] 



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 per- 

 haps some pepsin), and are lined by parietal cells. 



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 ( W. Stirling).] * J g- 185 ' 



The hydrochloric acid is formed, according to ^^f^f^^M^ 28 

 Heidenhain, by the parietal cells. It occurs on the expenmen %r %ng). 



free surface of the gastric mucous membrane as well as in the ducts of the fundus- 

 glands. The deep parts of the glands are usually alkaline. Free HC1 is detected 

 in human gastric juice, within 45 minutes to 1 to 2 hours after a moderate meal, 

 but in 10 to 15 minutes in a fasting condition after drinking water; the amount 

 gradually increases during the process of digestion. Lactic acid, perhaps derived 

 from the food, is found in the stomach immediately after taking food, after half an 

 hour along with HC1, while after an hour only HC1 is found (Ewald and Boas). 



CI. Bernard injected potassium ferrocyanide and afterwards lactate of iron into the veins of 

 a dog. After death, blue coloration 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. 



As 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. According to Voit, the formation of acid 

 ceases, if chlorides be withheld from the food. Maly suggests that the active 

 agent is lactic acid, which splits up sodium chloride and forms free HC1. The 

 base set free is excreted by the urine, rendering it at the same time less acid. 

 The formation of acid is arrested during hunger. According to H. Schultz, watery 

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

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



[The source of the HC1 is undoubtedly the sodic chlorfde in the blood and lymph, but what 

 other acid displaces the HC1 is a matter of conjecture. In this connection, it is important to 

 remember that Jul. Thomsen has shown that every acid can displace a part of another acid from 

 its combination with its base, and the weaker acid may even combine with the greater part of 

 the base. Thomsen calls this "avidity." Even strong mineral acids may be displaced by weak 

 organic ones. Thus the free C0 2 in the alkaline blood may set free a small quantity of HC1 from 

 the sodic chloride. "What is still more remarkable is, that the free HC1 should be transferred by 

 the cells towards the gland-duct, while the sodic carbonate diffuses towards the blood and lymph.] 



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



