998 THE ORGANS OF DIOKSTION 



and tliat it is possible for one organ to be elothed with peritoneum at the expense 

 of another. 



To complete the account of the general relation of the peritoneum to the intes- 

 tine, the following changes remain to be noticed: — 



The meso-colon. — The descending colon is displaced by the growth of the 

 rest of tilt' bowel to the left side, and comes to occupy the position which it holds 

 in the fully developed body. The i)rimitive meso-colon is displaced also to the 

 left, and survives as the descending meso-colon, the sigmoid meso-colon, and the 

 meso-rectum (fig. 599). It may be so curtailed that no distinct fold that can be 

 called a descending meso-colon is left, and the posterior part of the bowel is in such 

 a case found to be more or less uncovered by the peritoneum. The meso-rectum 

 is a genuine and but little disturbed relic of the simple median vertical fold of the 

 primitive body. 



Fig. 598. — Diagram to show the Relation of the Peritoneum to the Duodenum. 



A 



C. 



The duodenum is more or less bared of peritoneum, especially so far as its third 

 part is concerned. 



The ascending colon has, like the descending colon, been deprived of a con- 

 siderable amount of its peritoneum. This membrane originally belonged to the 

 common mesentery, but so much of it may have been abstracted from the bow^el 

 that this part of the colon may be free from peritoneum behind, or may be con- 

 nected to tlic posterior ])arietes by a short meso-colon. The parietal attachments 

 (so-called) of this ascending meso-colon are entirely acquired, and have no relation 

 whatever to tlu; ])rimary attachment of the median fold — the primitive meso-colon 

 — to tlie {)ostcrior wall of the a[)domen (fig. 599). 



The mesentery. — The mesentery proper — the fold belonging to the small 

 intestines — in like manner and by a similar process acquires a new connection with 

 the posterior parietes. Jn using the term ' new connection,' it must be understood 

 that the sac of the peritoneum remains quite unbroken, and that the numerous 

 duplicatures of the meml)rane have simply been so readjusted and disi)laced that it 

 has in more i)oints than one a refiexion from the posterior wall of the abdomen. 



