322 GLANDS OF THE STOMACH. [sect. 1 50. 



the name peptic cells (Frerichs). The cells situated in the uppermost parts 

 of the glands, which, as I find in man, are much smaller than the deeper 

 ones, as if they had arisen from the latter by division, are frequently dis- 

 charged externally, and are then directly concerned in the process of digestion ; 

 at other times, all, or almost all, remain in the glands during digestion, and 

 then the fluid part of the gastric juice, which passes outwards, extracts the 

 active material from them. The mucus of the stomach covers its whole surface 

 as a thicker or thinner coating, and is commonly more strongly marked at the 

 parts where the mucous glands are situated. It is derived — as Todd and 

 Bowman first correctly stated (Part iii., 1847, p. 192), and, as was subsequently 

 confirmed by Bonders and royself — from the cylindrical cells of the surface 

 of the stomach and interior of the mucous glands ; and either exudes from 

 them or is liberated by the dissolving and bursting of the cells, which 

 often cover the surface of the stomach in large quantities. It is still un- 

 certain how the epithelium is restored after the destruction of the cells, 

 which, however, do not seem to burst within the glands themselves. Probably 

 the epithelium-cylinders divide in the transverse direction before separation, 

 and only the outer portion is thrown off; and, in fact, we frequently observe 

 two nuclei in them. Probably, the cylinders also, as Todd and Bowman assume, 

 discharge their mucus without becoming detached, whilst they acquire a 

 temporary opening at the free extremity, as, in fact, is frequently observed 

 in cast-off cells. 



The stomach of birds, according to Berlin, contains several kinds of glands. 

 The well-known compound tubular glands of the glandular stomach — in which a 

 long, simple or branched central canal, with numerous simple perpendicularly 

 arranged tubes, is closely set with cylindrical epithelium — secrete, while these 

 cells are thrown off, a neutral juice containing pepsin. Small, simple tubes 

 with cylindrical epithelium, situated between these peptic glands form ordinary 

 mucus. There is a third form, lastly, in the muscular stomach, consisting 

 of long tubes with short cylindrical epithelium; which, moreover, are covered 

 by a structureless tunica intima, and whose ducts penetrate the horny epithe- 

 lium of this stomach ; these secrete a fluid acid juice, but no pepsin. Con- 

 sequently, as Berlin also showed by experiments on digestion, the two chief 

 constituents of the gastric juice are furnished by two special kinds of glands. 



§ 150. The tissue forming the mucous membrane, exclusive of the 

 glands, is, as we have already seen, very scanty. It appears only at 

 the bottom of the glands as a continuous, firm, reddish layer, 

 o*o22'" to o"044'" in thickness (Brileke), the muscular layer of the 

 mucous membrane, with interwoven bundles of ordinary areolar tissue 

 and smooth muscular fibres, the latter of which decussate especially 

 in two directions; and, in the pig, and as I observed recently, in man 

 also, even pass in between the glands and into the plicce villosce. 

 Besides, there exist between the glands, vessels, and an amorphous 

 connective substance without elastic fibrils, which forms, upon the 

 surface of the mucous membrane, a clear, perfectly homogeneous 



