sect. 157.] DEVELOPMENT OF THE ALIMENTARY CANAL. 231 



beautiful cylindrical epithelium. In the vermiform appendix, 

 the solitary follicles arc arranged close to each other; they arc 

 very frequent in the ccccura and rectum, and arc also more nume- 

 rous in the colon than in the small intestine. From those of the 

 latter part they are distinguished by their more considerable size 

 {%'", 1'" to i\'"), and by the circumstance, that upon each of the 

 small elevations of the mucous membrane which are occasioned by 

 the follicles, there exists, in the middle, a small pit-like, elongated, 

 or round opening, £"' to ^V" in diameter, which leads to a small 

 depression of the mucous membrane over the follicle. Bohmh&d in 

 his time allowed himself to be misled by these depressions, which are 

 never present upon normal follicles of the small intestine, and 

 regarded the follicles as follicular glands Avith openings, which, how- 

 ever, is incorrect ; for at the bottom of this depression there lies, as 

 Brilcke also observes, a completely shut, somewhat flat capsule, of 

 exactly the same structure as the follicles in the small intestine, 

 and also with vessels in the interior, as I recently found likewise 

 in man. 



The blood-vessels of the glands and follicles of the large 

 intestine present the same conditions as in the small intestine. 

 Around each Liebcrkuhnian opening there is a ring formed of 

 vessels croo6'" to croi'" in diameter, which is sometimes simple, 

 sometimes, especially in the neighbourhood of the solitary cap- 

 sules, multiple. From these vessels, wider venous trunks arise, 

 which pass inwards between the glands; whilst finer capillaries, 

 arising immediately from the arteries, form a dense network around 

 these (fig. 136). The relations of the lymphatics in the mucous 

 membrane are wholly unknown, as also those of the nerves. The 

 epithelium presents, throughout, the same conditions as in the small 

 intestine, and, at the anus, is marked off from the external epidermis 

 by a tolerably sharp border. 



§ 157. Development of the Intestinal Canal. — The whole intes- 

 tinal wall, however different it may subsequently appear, arises 

 from two formative parts, viz., 1. from the lower yerminal lamina 

 (mucous lamina, Pander- Baer ; mucous membrane, Reicherf ; 

 glandular lamina, or intestinal gland-lamina, Remak) , which is not 

 the basis of the entire mucus membrane, but only that of the 

 intestinal epithelium, and the intestinal glands; and 2. from 

 the middle germinal lamina (vascular lamina. Pander; mem- 

 brana intermedia, Reichert), which, besides many other parts 



z 



