ANATOMY OF THE MUCOUS COAT. 41 



part on each side of the gut in its interior, exists a transverse 

 doubling of the mucous coat forming the valvulae conniventes al- 

 luded to. The result of this arrangement is a semi-circular 

 valve on each side, one above the other, the margins of which 

 pass each other in the empty and contracted state of the rectum, 

 but touching at the same time, and they present an additional 

 barrier to the involuntary evacuation of faeces.* 



The large intestine is supplied with blood from a part of the 

 superior mesenteric, from the whole of the inferior mesentcric, 

 and from the internal pudic artery. Its veins empty into the 

 vena portarum. Its nerves are derived from the solar and the 

 hypogastrtc plexus of the sympathetic. 



SECT. III. ON THE MINUTE ANATOMY OF THE MUCOUS COAT OF 

 THE ALIMENTARY CANAL. 



In the preceding account of the mucous coat of the stomach 

 and bowels, I have admitted the most generally received opi- 

 nions, as it is in every way proper for medical men to be aware 

 of them. Having been, however, much occupied, a few years 

 ago, in ascertaining the pathology of Asiatic cholerat by dissec- 

 tions, the observations which I then made upon the healthy and 

 diseased structure have induced me to modify very much my 

 former views, as will be seen in the following pages. 



The mucous coat of the alimentary canal, in a healthy state, 

 and successfully injected, appears to consist, almost entirely of 

 a cribriform intertexture of veins. These veins being commonly 

 empty at death present themselves as a soft spongy structure, 

 which gives rise to the ordinary description of its sensible con- 

 dition as a velvety layer. The most minute injection of the ar- 



* It has latterly been advanced by Mr. O'Beirne, that in a natural state the 

 rectum is empty, and that the accumulation of faeces preparatory to a stool occurs 

 in the sigmoid flexure of the colon, where they are retained by a contraction of 

 the upper end of the rectum. The principal ground of this opinion!:!, that faecal 

 matter is rarely met with in the rectum. The observation is so contradictory to 

 my experience in the dissecting room and on patients, that I cannot but reject 

 it, though it appears to be obtaining some currency, or at least is quoted respect- 

 fully. Journal Hebd. 1833, vol. xiii. p. 126. Malgaigne, Anat. Chir. vol. 

 3d, 341. 



f Amcr. Journ Mod. Sciences for Vol. xvi. May, 1835. 



5* 



