1256 THE DIGESTIVE SYSTEM. 



the vena portse. In the sixth week, these two rudiments meet and unite with one 

 another, forming a long slender glandular mass which passes backwards within the dorsal 

 mesogastrium (meso-duodenum), between the vertebral column and the greater curvature 

 of the stomach. The pancreas, so formed, follows the changes which occur in the position 

 of the stomach and of the dorsal mesogastrium. Consequently its free dorsal extremity 

 comes to be directed to the left, while the right extremity or head is included within 

 the hollow of the curve formed by the duodenum. At first, it possesses a dorsal mesen- 

 tery, a part of the dorsal mesogastrium, but from the fifth month this disappears, 

 coincidently with the rotation of the gland into the transverse axis of the body. 



The lower part of the head, the body, and tail of the gland arise from the ventral 

 element, and the upper part of the head arises from the dorsal bud. 



The primary diverticula give off buds, lined with cylindrical epithelium, and these in 

 turn give off other buds, and the process goes on until the mass of the gland is formed. 



The islets of Langerhans are formed at a very early stage, from the entodermal lining 

 cells of the branching diverticula which form the gland acini. 



