52 THE MESENTERjr. 



of the large semicircular piece. In this case, the portions 

 like quadrants or sextants would assume a folded position like 

 the edge of the mesentery, while the middle of the semicircular 

 piece would preserve its regular form without folds ; as is the 

 case with the mesentery at some distance within its circumfer- 

 ence. By many additions of this kind, the circumference of a 

 membrane, which was originally a semicircle of five or six 

 inches, may be extended so as to exceed greatly that of tiie 

 mesentery. It seems of course impossible to form an accurate 

 model of the mesentery with a single piece of membrane or 

 paper; but it may be easily made with clay, or any ductile 

 substance. A model of this kind must necessarily be folded 

 after the manner of the mesentery ; and its circumference, like 

 the mesentery, would appear as if formed of portions of the 

 circumference of smaller circles united to each other.* 



The root of the mesentery commences with the jejunum on 

 the lower side of the mesocolon, at the left of the spine, and 

 extends downwards near to the right iliac region, crossing the 

 spine obliquely. When it is examined in its natural situation, 

 the peritoneum is found continued from the back of the abdo- 

 men to the intestine ; it then surrounds the intestine, and con- 

 tinues from it to the back of the abdomen again. There must 

 therefore be two lamina of peritoneum in the mesentery, and 

 there must be a small portion of intestine answering to the 

 interstice between these lamina which is not covered by the 

 peritoneum. The blood-vessels, and absorbents, or lacteals 

 pass most commodiously to the intestines between these lamina ; 

 for they are connected with large trunks that lie on or near the 

 spine, and the root of the mesentery commences there. 



The glands connected with the lacteals or absorbents are 

 very conspicuous in the mesentery, and are commonly called 

 mesenteric glands. They are of different sizes, from more than 

 half an inch to one or two lines in diameter. They are very 

 numerous, and scattered irregularly, but are seldom observed 



* A model, upon the plan first mentioned, was invented by Dr. J. G. Shippen. 

 It has been proposed, I believe by M. Gavard, to make one with a single piece 

 of buckskin, of a semitircular form, by stretching it at the circumference. 



