232 DIGESTION. 



are probably not exaggerated, though they are of necessity 

 merely approximative. 1 



This enormous quantity of fluid daily secreted by the 

 mucous membrane of the stomach would excite surprise were 

 it not considered that after this fluid has performed its office 

 in digestion, it is immediately reabsorbed, and but a small 

 quantity of the secretion exists in the stomach at any one 

 time. During digestion, a circulation of material is going 

 on, in which the stomach is continually producing, out of 

 materials furnished by the blood, a fluid which liquefies cer- 

 tain elements of the food, and, as fast as this is accomplished, 

 is absorbed again by the blood, together with the principles 

 that have been thus digested. 



Composition of the Gastric Juice. 



The gastric juice is mixed in the stomach with more or 

 less mucus secreted by the lining membrane. "When drawn 

 by a fistula, it generally contains particles of food which have 

 become triturated and partially disintegrated in the mouth, 

 and is always mixed with a certain quantity of saliva which is 

 swallowed during the intervals of digestion, as well as when 

 the stomach is in a state of functional activity. By adopting 

 certain precautions, however, the fluid may be obtained 

 nearly free from impurities, except the admixture of saliva. 

 The juice taken from the stomach during the first moments 

 of its secretion, and separated from mucus and foreign mat- 



1 In many works on physiology, the question of the quantity of gastric juice 

 secreted is very fully discussed. In the case of gastric fistula in a female, 

 already referred to (see p. 177), the quantity of fluid secreted in twenty-four hours 

 was estimated, from direct observations, at more than one-fourth the weight of the 

 body. (SCHMIDT, Ueber die Constitution des menschliclien Magcmaftes. Annal-en 

 der Chemie und Pharmacie, Heidelberg, 1854, Bd. xcii., S. 43.) In this case, it 

 was estimated that nearly nine thousand grains were secreted in an hour, and the 

 calculation for the twenty-four hours was made from this quantity. It is not 

 shown that the fluid thus collected was normal, either in quantity or quality ; and 

 even if it were, it is incorrect to suppose that its production in such quantity 

 continues during the twenty-four hours. These, and, indeed, all other estimates 

 made on the same principle, are entitled to but little consideration. 



