420 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



The primitive simplicity in the arrangement of the 

 mesentery is usually afterwards replaced by a more com- 

 plicated disposition, owing to the subsequent elongation 

 and consequent convolution of the intestine and stomach. 



The layer of peritoneal epithelium on the ventral 

 side of the stomach is continued over the liver, and 

 after embracing the liver, becomes attached to the 

 ventral abdominal wall. Thus in the region of the liver 

 the body-cavity is divided into two halves by a mem- 

 brane, the two sides of which are covered by the peri- 

 toneal epithelium, and which encloses the stomach 

 dorsally and the liver ventrally. The part of the mem- 

 brane between the stomach and liver is narrow, and 

 constitutes a kind of mesentery suspending the liver 

 from the stomach : it is known to human anatomists as 

 the lesser omentum. 



The part of the membrane connecting the liver with 

 the anterior abdominal wall constitutes the falciform or 

 suspensory ligament of the liver. It arises by a secondary 

 fusion, and is not a remnant of a primitive ventral 

 mesentery (vide p. 264). 



The mesentery of the stomach, or mesogastrium, 

 enlarges in Mammalia to form a peculiar sack known as 

 the greater omentum. 



The stomodseum. The anterior section of the per- 

 manent alimentary tract is formed, as in the Chick, by 

 an invagination of epiblast, constituting a more or less 

 considerable pit, with its inner wall in contact with the 

 blind anterior extremity of the mesenteron. 



From the epiblastic liniog of this pit are developed 

 the pituitary body and the salivary as well as the other 

 buccal glands. 



