t. rtut.poit. 



roe, post 



rtu.pt St. 



FIG. 515. TRANSECTION OF THE SPINAL CORD OF AN EMBRYO CHICK. 



c. rad. ant., axons to the ventral roots; c. rad. post., axons to the dorsal roots; 

 col, collateral from an axon back to the gray matter; gg, dorsal root ganglion; rac. 

 ant., ventral root; rac. post., dorsal root. (After van Gehuchten.) 



Head fold' 



Neuropore 



Pharynx 



Vitellin vein-,..... < 



Medullary groove 



Anterior cerebral 



vesicle, or pros- 

 encephalon 



Mesodermic 



somite 



FIG. 516. RECONSTRUCTION OF THE ANTERIOR PORTION OF THE BODY OF A YOUNG 

 CHICK EMBRYO, SEEN FROM THE DORSAL SURFACE. (After Kollmann.) 



593 



