THE ORGANS OF THE INNER GERM-LAYER. 



299 



The embryonic processes of growth in the case of the alimentary tube shed 

 light on the asymmetrical position of the two nervi vagi, which pass through 

 the diaphragm, the left on the front side of the oesophagus to be distributed 

 to the front side of the stomach, the right on the back side of the oesophagus 

 to the corresponding surface of the stomach. If we imagine the process of 

 torsion in case of the oesophagus and stomach to be reversed, the symmetry in 

 the course and distribution of the vagi will be completely restored. 



The torsion of the stomach naturally exercises a great influence on 

 the mesogastrium, and, as JOH. MULLER was the first to show clearly, 



'.'7 



Tig. 165. Diagram of the development of the human alimentary canal and its mesentery. 



A, earlier. S, later stage. 



gn, Greater omentum, which is developed from the mesogastrium (fig. 164 mg). The arrow 



indicates the entrance to the omentum (bursa omentalis). gc, Greater curvature of the 



stomach ; gg, ductus choledochus ; du, duodenum ; rn.es, mesenterium ; me, mesocolon ; 



dd, small intestine ; di, large intestine (colon) ; md, rectum ; dg, vitelline duct ; bid, coecum ; 



iff, appendix vermiformis ; it, place where the loops of the intestine cross each other. The 



colon with its mesocolon crosses the duodenum. 



initiates the development of the greater omentum (omentum ma jus). 

 As long as the stomach has a vertical position, its mesentery is a 

 vertical lamella, which stretches from the vertebral column (fig. 164) 

 directly to the greater curvature, that is still directed backward 

 [dorsad]. But in consequence of the torsion it becomes greatly 

 stretched and enlarged, because its attachment to the stomach must 

 follow all the displacements of that organ. From its origin at the 

 vertebral column, it therefore now betakes itself to the left and 

 downward to become attached to the greater curvature of the 

 stomach ; it assumes a shape and position of which the reader will 

 easily form a correct idea if he mentally combines the diagram of 



