THE PKRITOXFJM 



9i>7 



parietes has nover closed, and tlic })rittrudiii<: looj) of l)owi'l has never heen quite 

 witluh'awn into tlie al)don)en. The sae of such a hernia is made out of the tissues 

 of the Tuiibilieal cord, and the contents are usually the c;ecuni and lower ]»art of 

 the ileum, and not infrequently a Meckel's diverticulum. As has been mentioned 

 already, the ciecum may l)e found near the middle line or in the right hypochon- 

 driac region (page 971). It is then spoken of as undescended. 



Final changes in the peritoneum. — Further changes in the position of the 

 intestine and in the arrangement of the peritoneum are finally l)r()Ught about, and 

 these changes are almost entirely limited to the human subject. The intestine 

 grows, and other abdominal viscera are encroaching upon the {leritoneum. This 

 membrane is mol)ile, is easily drawn from one ])oint to another, and is capable of 

 consideral)le adjustment. It does not, however, continue to grow at the same rate 

 as the viscera which it serves to cover. The peritoneum is relatively more extensive 

 in the frtus than in the adult, and in the lower mammals than in man. 



If the viscera grow out of proportion to the peritoneuu), it is evident that the 

 reflections of that membrane must here and there be shortened; and it is possible 

 that a viscus which was at one time entirely covered by i)eritoneum may in due 

 course become almost bared of it. This is so. In the diagram (fig. 598) a trans- 

 verse section of the body is imagined, the section traversing the spot where the 

 duodenum and transverse colon are in relation at the neck of the great comn)on 



Fig. 5S>7. — Uiagkam to show thk Rotation of the Intestinal Canal. 



mesentery. Here, by reason of the rotation of the intestine from left to right, the 

 mesenteric lamina has become folded ujjou itself (A, fig. 598). The fold would 

 be V-sha))ed, ojjcn al)ove, but coming to a point below. On transverse section the 

 meso-duodenum (m-d) and transverse meso-colon (m-c) can be seen side by side. 

 Now a constantly increasing demand upon the peritoneum is made by the rapidly 

 growing viscera. The meml)rane is drawn in this directi(jn and in that. There is 

 some symmetry, however, within the abdomen, and the mendjrane may be 

 conceived to be drawn ecjually upon in the direction of the arrows r and l. 



The result of such traction upon the |)eritoneum in this particular instance will 

 be to lessen the length of the transverse meso-colon, and to use up the meso-duo- 

 denum altogether (fig. 598, B). That piece of bowel is indeed at last left uncovered 

 by peritoneum behind, and is brought into contact with the ])osterior ])arietes. The 

 serous membrane which formed the nu'so-duodenum has been utilised to ali'ord a 

 covering for adjacent viscera, which are increasing in size, and are pushing the peri- 

 toneum before tliem as they advance. In this particular region of the abd(»men 

 the growth of the liver, stomach, anil sideen make great demands u]»on the adjacent 

 jK'ritoneum. As has been already said, it is evident that the growth of the general 

 sac of the peritoneum does not keei> pace with the growth of the structures it covers, 



