162 



ALIMENTAKY CANAL 



and consists of a proximal descending and a distal ascending limb. As il 

 increases in length the two limbs come close together, and the posterk 

 extremity (afterwards the middle of the transverse colon) is brought into clos 

 relationship with the end of the duodenal loop (fig. 204). Very early a rotatioi 

 of the loop commences round its long axis, which brings the distal over th< 

 proximal limb. On the distal limb an evagination develops which is th< 

 rudiment of the caecum (fig. 204), and from now onwards it is possible 

 distinguish the portion of the gut which will become the small, from that whicl 



1st thoracic nerve 

 -2nd thoracic vert. 



pericardium 



lung 



-adrenal 



1st lumbar nerve 



stomach 



liver 



- kidney 



~ Woljfianbody 



mesentery urogenital sinus 

 FIG. 205. KECONSTBUCTION OF A HUMAN EMBBYO OF 24 MM. (After Mall.) 



will become the large intestine. The small intestine increases in length more 

 rapidly than the large intestine, and, while still without the body-wall, it begins I 

 to be coiled (fig. 205). It shows six bends which presently become six primary 

 circular coils (Mall). The distal coil ends at the ca3cum, and from this the large 

 intestine passes straight back in the middle line to the back wall of the abdomen, 

 where it turns sharply down to end in the rectum (fig. 206). As the result of the 

 continuance of the axial rotation, the small intestine becomes displaced to the 

 left, under the large intestine and below the superior mesenteric artery, until it 

 assumes its definitive position, while the large intestine, also increasing in length, 



