ON THE DIGESTIVE FUNCTION, &c. 



129 



This wonderful menstruum, the "most active we are acquainted with in 

 nature, is secreted by a distinct set of vessels that exist in the texture of the 

 stomach, and empty themselves into its cavity by innumerable orifices invi- 

 sible to the naked eye ; and it is hence called gastric juice, from yaffr^, which 

 is Greek for stomach. Mr. Cruickshank supposes about a pound of it to be 

 poured forth every twenty-four hours. " The drink," says he, " taken into 

 the stomach may be two pounds in twenty-four hours ; the saliva swallowed 

 ma}'' be one pound in the same period, the gastric juice another, the pan- 

 creatic juice another. The bile poured into the intestines Haller supposes 

 about twenty ounces^ besides the fluid secreted through the whole of the 

 internal surfaces of the intestines which Haller calculates at not less than 

 eight pounds in twenty-four hours, — a calculation, nevertheless, that Blumen- 

 bach regards as extravagant.f 



The quantity of the gastric juice, however, seems to vary very considerably, 

 according to the demand of the system generally, or the state of the stomach 

 itself. In carnivorous birds, whose stomachs are membranous alone, and, 

 consequently, whose food is chymified by the sole action of the gastric juice, 

 without any collateral assistance or previous mastication, this fluid is secreted 

 in much larger abundance ; as it is also in those who labour under that 

 morbid state of the stomach which is called canine appetite ; or when, on 

 recovery from fevers, or in consequence of long abstinence, the system is 

 reduced to a state of great exhaustion, and a keen sense of hunger induces a 

 desire to devour food voraciously and almost perpetually. 



Such was the situation of Admiral Byron and his two friends, Captains 

 Cheap and Hamilton, after they had been shipwrecked on the western coast 

 of South America, and had been emaciated, as he tells us, to skin and bone, 

 by having sufi'ered with hunger and fatigue for some months. "The go- 

 vernor," says Admiral Byron, " ordered a table to be spread for us with cold 

 ham and fowls, which only we three sat down to, and in a short time des- 

 patched more than ten men with common appetites would have done. It is 

 amazing that our eating to that excess we had done from the time we first 

 got among these kind Indians had not killed us ; we were never satisfied, and 

 used to take all opportunities, for some months after, of filling our pockets 

 when we were not seen, that we might get up two or three times in the night 

 to cram ourselves."! 



When pure and in a healthy state, the gastric juice is a thin, transparent, 

 and uninflammable fluid, of a weak saline taste, and destitute of smell. 

 Generally speaking, it is neither acid nor alkaline ; but it appears to vary 

 more or less in these properties, not only in animals whose organs of diges- 

 tion are of a different structure, but even in the very same animal under dif- 

 ferent circumstances. It may, however, be laid down as an established rule, 

 ih3.tin carnivorous andgrandnivorous animals possessing only a single stomach, 

 this fluid is acid, and colours blue vegetable juices red ; in omnivorous animals, 

 as man, whose food is composed both of vegetable and animal diet, it is neu- 

 tral ; and in graminivorous ruminating animals with four stomachs, and par- 

 ticularly in the adults of these tribes, it has an alkaline tendency, and co- 

 lours blue vegetable juices green. 



There are two grand characteristics by which this fluid is pre-eminently 

 distinguished ; a most astonishing faculty of counteracting and even correct- 

 ing putrefaction; and a faculty, equally astonishing, of dissolving the tough- 

 est and most rigid substances in nature. 



Of its ANTISEPTIC POWER abuudaut proofs may be adduced from every class 

 of animals. Among mankind, and especially in civilized life, the food is usu- 

 ally eaten in a state of sweetness and freshness ; but fashion, and the luxuri- 

 ous desire of having it softened and mellowed to our hands, tempt us to keep 

 several kinds as long as we can endure the smell. The wandering hordes of 

 gypsies, however, and the inhabitants of various savage countries, and espe- 



* Anat, of the Absorbing Vessels, p. 100. t Physiol, InstUut, xxvii, $ 410- 



t Voyage, p, 181. See also Hunter's Animal Economy, p, 196. 



