GASTRIC DIGESTION. 



417 



Fig. 125*. 



[The function of these tubular glands, according to Dr. Kirkes, appears to be 

 the production of cells containing the digestive or gastric fluid. When the 

 stomach is empty, the glands appear to be at rest ; they are called into action 

 by the introduction of food. Their walls consist essentially of tubular inflec- 

 tions of the basement membrane of the mucous coat of the stomach; during 

 active digestion they are filled with cells, in various stages of development, 

 engaged in the elaboration of gastric fluid. 



In the production of these cells minute granules appear to be generated at 

 the deeper part of each gland ; two or more of these granules, grouping together, 

 form nuclei, and are developed into nucleated cells. In those parts of the gland 

 which are nearest to the free surface, secondary cells are developed without the 

 primary ones; the walls of the latter then appear to coalesce and form the proper 

 membrane of the gland, while the new generation of 

 cells, filled with gastric fluid, are discharged and mixed 

 with the food in the stomach (Fig. 125*). 



According to Bernard, the elaboration of the gastric 

 fluid in these cells seems to be completed only when they 

 reach the surface, for, according to this observer, the 

 mucous membrane is not acid a little below the surface. 

 It has been suggested by Dr. Brown-Sequard, however, 

 that these glands may be concerned in the elaboration 

 of some other constituent of the gastric juice the pep- 

 sin, for instance; while the acid constituents are de- 

 veloped by some of the other follicles that stud the 

 mucous membrane of the stomach. 



When the stomach is empty and inactive, the glands 

 are said to be also inactive and empty, and to have their 

 walls lined with cylindrical epithelium similar to that 

 by which the whole surface of the stomach is covered 

 during the intervals of digestion. 



The presence of this epithelium in the tubular glands 

 usually closes their orifices, so that during fasting they 

 are often distinguishable only as minute, slightly pro- 

 minent papillae. When the glands again commence 

 secreting, the epithelium separates from the deeper 

 part, and together with some of that covering the 

 mucous surface of the stomach, is mixed up with 

 the newly-formed cells containing the gastric fluid. 1 

 ED.] 



441. The nature and composition of the Gastric Juice which is secreted and 

 poured forth by this follicular apparatus, have been the subjects of much dis- 

 cussion among Chemists; and though certain points may be considered as satis- 

 factorily determined, there are others which still remain doubtful. This liquid, 

 when obtained without admixture with saliva, is clear, transparent, colorless or 

 slightly yellow, and has very little viscidity. Its specific gravity is not much 

 above that of water; and according to the analysis of Frerichs, it does not con- 

 tain above 1.72 per cent, of solid matter, of which more than half seems to 

 consist of the peculiar "ferment" to be presently described, the remainder 

 being composed of chlorides and phosphates of potass, soda, lime, and magnesia. 

 Microscopic examination indicates the persistence of a few of the cells exuviated 

 from the interior of the gastric follicles ; but these for the most part leave no 

 other traces than their nuclei and a fine molecular matter arising from* their 



One of the tubular follicles 

 of the pig's stomach, after Was- 

 mann, cut obliquely so as to 

 display the upper part of the 

 cavity, with the cylindrical epi- 

 thelium forming its walls. At 

 the lower part of the follicle, 

 the external nucleated extremi- 

 ties of the cylinders of epithe- 

 lium are seen. 



27 



" Kirkes and Paget's Manual of Physiology," p. 166, Am. Ed. 



