26 LABORATORY OUTLINES FOR EMBRYOLOGY 



the coelome, or body cavity. How many dorsal aortae 

 are here? Is the ventral aorta present in this section? 

 Why? Between the body cavity and the outside of 

 the body on either side is a blood vessel. If this 

 blood vessel be traced through the different sections, it 

 will be seen that it connects the cardinal veins with the 

 heart. It is the duct of Cuvier. It is formed by the 

 union of the anterior and posterior cardinal veins and 

 empties into the heart near the place where the vitel- 

 line veins join the heart. Identify the myocardium 

 and the endocardium. 



Draw the section, color the different germ layers, and 

 label all the parts. 



(4) Through the Embryo about Half Way between the Heart and 

 the Posterior End 



Note the beginning of the folding up of the somato- 

 pleure to form the amnion. The point on each side 

 where the lateral fold delimits the embryonic from the 

 extra-embryonic area is the lateral limiting sulcus. What 

 is the character of the mesoblastic somites? How have 

 the myotome and sclerotome been formed? On the dorsal 

 surface of the nephrotome is a thick cord of cells with a 

 small hole in it. This is the Wolffian duct or mesonephric 

 duct. How many dorsal aortae ara there? Are the cardi- 

 nal veins found in this section? If they are present, 

 they are called the posterior cardinal veins. 



Draw the section, color the different germ layers, and 

 label all the parts. 



