326 SURGICAL APPLIED ANATOMY. [Chap. xvn. 



childhood, and a freer escape of the intestines from 

 the abdomen is allowed in subjects under puberty. 

 The disposition of the membrane permits also a freer 

 downward excursion of the bowels on the right side, 

 and this has been offered as an explanation of the 

 undue frequency of right-sided inguinal hernise in 

 childhood (Lockwood). 



The root of the mesentery, and, indeed, the whole 

 of the peritoneum covering the posterior abdominal 

 wall, may glide a little downwards and constitute a 

 " prolapse of the mesentery." This condition has been 

 fully investigated by Mr. Lockwood, who states that 

 it seldom occurs before middle age, that it causes the 

 mass of the intestines to incline to the left and thus en- 

 courages double and left-sided hernia?. These hernia? 

 are well known to be more common after middle age. 



Mr. Lockwood states that in acquired hernia the 

 mesentery is found to have had its attachments 

 lowered rather than to have been increased in length. 



Certain holes are sometimes found in the mesen- 

 tery, through which intestine has been strangulated. 

 Some of these holes, especially those that are slit-like, 

 are due to injury, others are due to congenital defect 

 of the mesentery. I have shown that the latter holes 

 are round, are in the mesentery of the lower ileum, 

 and occupy an oval area, circumscribed by an anasto- 

 motic arch between the ileo-colic branch of the superior 

 mesenteric artery and the last of the intestinal arteries. 

 This area is often the seat of atrophied peritoneum, 

 and shows an absence of fat, of visible blood-vessels, 

 and of glands. It would be easy for a knuckle of gut 

 to be forced through the thinned membrane, which is 

 sometimes already cribriform. 



For an account of "mesenteric hernia" see 

 page 339. 



Herm'se have nocurred through the foramen of 

 Winslow. 



