ii EXTERNAL DIGESTIVE SECRETIONS 105 



of internal secretion. Lornbroso's observations indicate a constant 

 relation between the degree of glandular degeneration in cases 

 when a segment is grafted under the skin, and its function before 

 and after excision. The less the segment is altered, the better it 

 accomplishes its internal function, and the more acute are the 

 effects of extirpation. 



All this evidence is at present" too inconclusive to determine 

 whether the internal secretion of the pancreas is exclusively 

 confined to the islets of Langerhans, or if the alveoli also 

 contribute to it. This question must be left in abeyance for 

 future research. 



XL The walls of the Stomach, in a vertical section, show four 

 coats or layers, known from without inwards as the serous, 

 muscular, submucous (or areolar) and mucous membranes 

 (Fig. 33). 



The mucous membrane of the stomach, which alone concerns 

 us, is in two parts, the pyloric end, which is pale in colour, 

 with fewer longitudinal folds, and the 

 fundus, which is reddish, yellow, or brown, 

 with more frequent and irregular folds 

 forming a network. Beside these coarse 

 folds (which are obliterated when the organ 

 is distended with food), a lens shows pro- 



*- , FIG. 34. Epithelium of surface 

 jectlOllS On the internal SUriaCe Ol the of stomach examined fresh. 



stomach, with corresponding depressions of gg y magnili 

 polygonal shape, which become larger and 



deeper near the pyloric orifice. These are the mouths of the 

 tubular glands with which the gastric nmcosa is beset. 



Taken as a whole, the columnar epithelial cells which cover the 

 mucous membrane of the stomach (Fig. 34), may be regarded as a 

 secreting organ which is not, like the glands we have been 

 discussing, gathered into a small space, but is spread out over the 

 surface. The function of this secreting surface does not differ 

 specifically from that of the simple and compound mucous glands 

 found in the buccal cavity and along the mucous membrane of the 

 oesophagus. The columnar epithelial cells of the stomach are, 

 however, richer in albumin than the mucous cells of the sub- 

 maxillary gland, and behave very differently from them when 

 treated with acetic acid ; they do not become clouded, but are 

 clear and swollen. With mineral acids, and on hardening with 

 alcohol, the submaxillary cells scarcely cloud at all, while those of 

 the gastric epithelium become quite turbid (Heidenhain). 



The appearance of the columnar epithelium differs to a marked 

 extent in the state of rest and of digestive activity. In the 

 latter, many of the cells become goblet-shaped, open to the out- 

 side, and half -empty, owing to escape of the niucin which is 

 elaborated from the mucinogen formed inside the cell. 



