. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. STOMACH AND INTESTINE. 351 sence occurs in the agminate follicles, or " Peyer's ; Here they are absent over the several follicles which together form each patch ; and become short, (a, Jig. 21*2, p. 358.) blunt, irregular, or even confluent, where they occupy their interstices. We have seen that each of the valvulae conniventes is a doubled fold of membrane, separated by a layer of areolar tissue. While the minute intestinal tube may almost be re- garded as a mere membranous lamina, which is involuted s
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. STOMACH AND INTESTINE. 351 sence occurs in the agminate follicles, or " Peyer's ; Here they are absent over the several follicles which together form each patch ; and become short, (a, Jig. 21*2, p. 358.) blunt, irregular, or even confluent, where they occupy their interstices. We have seen that each of the valvulae conniventes is a doubled fold of membrane, separated by a layer of areolar tissue. While the minute intestinal tube may almost be re- garded as a mere membranous lamina, which is involuted so as to surround a cylindrical cavity, and is packed in a sparing fibrous invest- ment. But the villus constitutes, as it were, a solid process of the mucous membrane. In accordance with this structure, it consists of an epithelium, a basement membrane, a stroma or basis of fibrous tissue, unstriped muscle, and numerous blood-vessels. And in ad- dition to these constituents, which may be found under various modifications throughout the whole intestinal mucous membrane, the interior of each villus encloses one or more branches of the lacteal vessels which con- tain the chyle. The epithelium of the villi (a, fig. 259. and a, figs. 26-i, 265,266.) consists of a single layer of cylindrical cells, which,—as regards size, shape, and general appearance, — closely resemble those seen on the ridges between the tubes of the stomach. They are, how- ever, even more delicate in their structure, as well as more conical in their shape. fig- And their contents are, even during fasting, somesvhat darker and more granular. The nucleus, which occupies the same situation in both these varieties of cylindrical epi- thelium, contains a single bright spot, or nucleolus : in rare instances, this appears to be double. The basement-membrane (at b, Jig. 260.) docs not require any special mention. As in the gastric ridges, it is very closely at- tached to the subjacent structures, espe- cially to the
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