GENERAL ANATOMY OF THE MUCOUS MEMBRANES. 51 



A mucous membrane presents two surfaces, one of which ad- 

 heres to the contiguous parts, and the other is free by being in- 

 ternal. The adherent surface is attached by a cellular structure 

 somewhat condensed. This cellular structure is principally re- 

 markable for its want of disposition to secrete fat into its inter- 

 stices; a property of immense importance, as without it, ob- 

 structions would be continually occurring to the destruction of 

 life : it is pervaded by a multitude of fine vessels and nerves, run- 

 ning forward to be spent upon the mucous membrane ; and has 

 been unfortunately named nervous coat, by anatomists of high 

 authority. The strength of attachment which it furnishes is 

 somewhat varied; for example, in the small intestinal canal 1 

 have often seen the mucous membrane caught at one end and 

 entirely withdrawn from the muscular coat, an experiment which 

 alone can give rigid ideas of its greater length, as by it all the du- 

 plicatures or valvulae conniventes are stretched out. The ex- 

 periment succeeds much more certainly by the regular pressure 

 of a column of water between the tunics of the intestine. The 

 mucous membrane of most organs is arranged into wrinkles and 

 duplicatures, for the purpose of augmenting its extent. This ar- 

 rangement prevails in the nose, and, as mentioned, in the oeso- 

 phagus, in the stomach and intestines: to say nothing of many 

 other instances which are noticed in the description of each 

 organ. In some examples, they are permanent, and, in others, 

 depend on the state of contraction of an exterior muscular coat. 

 The interior face of the mucous membranes, allowance being 

 made for the inequalities just stated, moreover, presents, when 

 closely viewed, an abundance of more minute depressions and 

 of elevations, causing it to resemble velvet. Some of these de- 

 pressions are so large as to give it a cellular appearance,* as in 

 many parts of the intestinal canal, and in the gall-bladder, and 

 have been particularly described by Sir Everard Home. 



In regard to organization, the mucous membranes are of a 

 soft, spongy consistence; easily yield to mechanical violence; 

 and depend for their strength upon the surrounding cellular coat. 

 They are not of a uniform thickness; for example, they are much 

 thinner in the urinary and genital apparatus, than in the alimen- 

 tary canal; they also present some varieties of consistence. They 



* They are not to be confounded with the follicles, but are a miniature repre- 

 sentation of what is called tripe, in culinary language. 



