INTESTINE 



161 



straight (fig. 199, A, Mg], soon begins to show the convexity of the greater curvature 

 on the side next the vertebral column, and the concavity of the lesser curvature 

 on the opposite border (fig. 203, B, Mg), while the pyloric end becomes tilted away 

 from the vertebral column, producing the duodenal loop (fig. 203). Finally 

 the organ becomes turned over on what was previously its right side, which now 

 becomes the posterior surface ; and the pyloric extremity being also tilted over, 

 the duodenal loop is thrown over to the right side of the abdomen (fig. 204). 

 The section of the gut between the stomach and the mouth of the yolk-sac is at 



Sth cervical nerve 

 1st thoracic vert. 



pericardium 



adrenal 



stomach 



12th thoracic nerve 



Wolffian body 



kidney 



5th lumbar nerve 



I i 



sm. intest. caecum 



grt. intest, w.d. ur 



FIG. 204. RECONSTRUCTION OF A HUMAN EMBRYO OF 17 MM. (After Mall.) 

 bl, bladder ; w.d., Wolffian duct ; ur, ureter. 



first short and straight. It early shows a forward directed diverticulum which-fis 

 the rudiment of the liver. It gradually increases in length by the closure of the 

 mouth of the yolk-sac, until the whole length of the intestine is laid down as a nearly 

 straight tube which is attached to the posterior wall of the primitive abdominal 

 cavity by a continuous mesentery (fig. 203, A). As the liver develops and comes 

 to occupy a large section of the cavity, the intestine, increasing in length, forms a 

 loop which extends through the wide-open umbilicus (fig. 204). This loop 

 (vitelline loop) gives attachment at its extremity to the vitelline stalk (fig. 203), 



VOL. I. 



M 



