THE GASTRIC JUICE. 129 



in terms of hydrochloric acid. In clinical work it is customary to 

 express the degree of acidity in terms of the number of c.c. of T n ^ 

 alkali solution which would be necessary to neutralize 100 c.c. of 

 stomach -con tents. 



Degree of Acidity. The degree of acidity of the gastric juice 

 is usually fairly constant, and in man varies between 0.3 and 0.5 

 per cent. As has been stated, it is influenced to a great extent by 

 the character of the diet. Following the administration of a meal 

 rich in albumins, larger amounts are obtained than after the inges- 

 tion of carbohydrates or fats. The smallest amounts are found 

 after the ingestion of water. After Ewald's test-breakfast, which 

 consists of from 35 to 70 grammes of wheat bread and 300 to 

 400 c.c. of water, or weak tea without sugar, the maximum acidity 

 is reached in about one hour, and corresponds to 1.5 to 1.75 pro 

 mille. Following the ingestion of RiegeFs test-meal, on the other 

 hand, which consists of a plate of soup (400 c.c.), 200 grammes of 

 beefsteak, 50 grammes of wheat bread, and 200 c.c. of water, the 

 amount of hydrochloric acid increases to 2.7 pro mille, after from 

 one hundred and eighty to two hundred and ten minutes. In disease 

 still higher figures (5 p. in.) may be observed ; or its secretion may 

 diminish below the normal, and may even cease altogether. 



Hydrochloric Acid. Origin. The hydrochloric acid of the 

 gastric juice is furnished by the parietal, adelomorphous, or oxyntic 

 cells, which are principally found in the glands of the middle 

 region of the stomach. In the pyloric region, where these are 

 absent, the reaction is alkaline, and in the fundus also, where they 

 are either absent or present in greatly diminished numbers, the 

 secretion is not acid. 



While it is thus quite probable that the hydrochloric acid is fur- 

 nished by the parietal cells, we are ignorant of the mechanism by which 

 this is accomplished. A free acid is manifestly not present in these 

 cells, as can be shown by testing with litmus-paper, or still better by 

 injecting potassium ferrocyanide and lactate of iron into the circula- 

 tion of an animal, when it will be observed that Berlin-blue is 

 formed in the stomach-cavity, while the cells themselves remain 

 unstained. It thus follows that a substance must either be present 

 in the cells which is capable of yielding hydrochloric acid when 

 secreted to the outside, or a mechanism must exist by which the 

 hydrochloric acid, though formed within the cells, is at once elim- 

 inated. The latter view is now generally held. That the hydro- 

 chloric acid is derived from the chlorides of the blood can be 

 regarded as an established fact. It may thus be secreted even 

 though no food-stuffs have been ingested ; and Kahn has shown 

 that animals in which the chlorides of the body have been 

 artificially reduced to that minimum which is tenaciously retained 

 are no longer capable of secreting hydrochloric acid. Ludwig for- 

 merly thought that hydrochloric acid resulted through electro- 

 lytic influences within the cells, and that the acid then dif- 

 9 



