GENERAL ANATOMY OF THE MUCOUS MEMBRANES. 53 



thin laminae, having a tufted arrangement. Those of the jeju- 

 num are long and narrow, having more the form commonly as- 

 signed to them, while in the lower part of the ileum and in the 

 colon they again become laminated. x 



It should be observed that notwithstanding the assertion of 

 Lewenhoeck, Hewson, Hunter, and others, the fact is still called 

 in question, by two of the most distinguished anatomists of the 

 present time, MM. Beclard and J. F. Meckel, whether the orifices 

 of the lacteals are, under any circumstances, visible on the sur- 

 face of the villi. Admitting that they do not open as stated, the 

 power of interstitial absorption in the mucous membrane will 

 still account for the chyle finally getting into the lacteals, as well 

 as for fluids passing into the circulation from the stomach, when 

 its continuity with the intestinal canal has been interrupted.* 



The Epidermis or Epithelium of mucous membranes is very 

 distinct at their external orifices, but becomes less and less ap- 

 parent towards the interior of the body, until it finally cannot be 

 distinguished; and anatomists generally consider that it is entirely 

 deficient, notwithstanding the assertion of Haller to the contrary. 

 It is a matter of common observation, that when the interior of 

 mucous membranes is exposed by an eversion for a long time, to 

 the action of the atmosphere; they take on more of the structure 

 of skin, and become evidently covered with a cuticle which pro- 

 tects them and diminishes their secretion. This is exemplified 

 in eversion of the vagina from prolapsed uterus, in elongated and 

 tumid labia interna, and in other ways : restore the parts to their 

 natural situation, and they are brought back to their original 

 structure. In the partial prolapse of the mucous membrane of the 

 rectum, from piles, corresponding circumstances occur. From 

 this we infer, that the full development of cuticle depends very 

 much upon the degree of exposure which any surface of the 

 body has to undergo. The reverse also takes place : shut up or 

 close any surface of the skin so that it is put in the condition of 

 an interior cavity, and it immediately begins to assimilate it- 

 self to a mucous membrane. This is proved by the tendency in 

 young children to a detachment of the cuticle, or excoriation of 



* Should the suggestion of the absorbing 1 powers of the gastro-enteric follicles 

 which I have proposed in Section third, be correct, it will dispose of the difficul- 

 ties and opposing opinions alluded to in this paragraph. 



6* 



