578 DIGESTION, 



organic functions, " doubtless for the purpose of harmonizing them 

 -with each other, and with the conditions of the organs of animal life." 1 



The gentle, oscillatory or vermicular motion of the stomach, and the 

 admixture with the fluids, secreted by its internal membrane, as well as 

 by the different follicles, &c., in the supra-diaphragmatic portion of the 

 alimentary canal, are probably the main agents in the digestion ope- 

 rated in the stomach. 



Much contrariety of sentiment has existed regarding the precise 

 organs that secrete the fluid which oozes out as soon as food is placed 

 in contact with the mucous coat of the stomach. Whilst some believe 

 it to be exhaled from that membrane ; others conceive it to be secreted 

 by the numerous follicles, seated in the membrane as well as in that of 

 the lower portion of the oesophagus; or by what have been termed gas- 

 tric glands. The analogy of many animals, especially of birds, would 

 render the last opinion the most probable. In them we find, in the 

 second stomach, the cardiac or gastric glands largely developed ; and it 

 is probable, that they are the great agents of the secretion of the digest- 

 ive fluid. (See Figs. 228 and 229.) MM. Tiedemann and Gmelin 2 affirm, 

 that the more liquid portion of the gastric fluid is exhaled, and that the 

 thicker, more ropy and mucous portion is secreted by the follicles, 

 Rudolphi 3 assigns it a double origin ; from exhalants, and gastric 

 glands; whilst MM. Leuret and Lassaigne 4 ascribe its formation exclu- 

 sively to the villi. Dr. Beaumont, 5 who had an excellent opportunity 

 for experimenting on this matter, remarks, that on applying aliment, or 

 any irritant, to the internal coat of the stomach, and observing the 

 effect through a magnifying-glass, innumerable minute, lucid points, and 

 very fine papillae, could be seen protruding, from which a pure, limpid, 

 colourless, slightly viscid fluid distilled, which was invariably and dis- 

 tinctly acid. On applying the tongue to the mucous coat in its empty, 

 unirritated state, no acid taste could be perceived. Although no aper- 

 tures were perceptible in the papillae, even with the assistance of the 

 best microscope that could be obtained, the points, whence the fluid 

 issued, were clearly indicated by the gradual appearance of innumera- 

 ble very fine, lucid specks, rising through the transparent mucous coat, 

 and seeming to burst, and discharge themselves upon the very points 

 of the papillae, diffusing a limpid, thin fluid over the whole interior gas- 

 tric surface. 



A like difference of opinion has prevailed regarding the chemical 

 character of the fluids ; and this has partly arisen from the difficulty 

 of obtaining them identical. The true fluid secreted by the gastric fol- 

 licles or mucous membrane can never, of course, be obtained for examina- 

 tion in a state of purity. It must always be mixed not only with the 

 other secretions of the stomach, but with all those transmitted to the 

 organ, by the constant efforts of deglutition. It is, consequently, to 

 this mixed fluid, that the term gastric juice has really been applied ; 

 although it is more especially appropriated to the particular fluid, pre- 

 sumed to be secreted by the stomach, and to be the great agent in diges- 



1 Human Physiology, p. 151,Lond., 1842. 2 Op. citat. 



3 Grundriss der Physiologie, 2 er Band, 2<e Abtheilung, s. iii., Berlin, 1828. 



4 Recherches sur la Digestion, Paris, 1825. 5 Op. citat., p. 103. 



