SECOND HALF OF SECOND DAY 



479 



depression formed in it which is to become the infundibulum. This is 

 an important seat of future development. It must, therefore, be studied 

 carefully so that it can be recognized in future work. 



lv 



le 



Fig. 283. 



I. Views to show the posterior displacements of the heart in the chick 

 embryo. A, The heart lies ventral to the first segment. This is the region where 

 the future hindbrain will form. B, The point of bending loop of the ventricle is 

 at the seventh cervical segment. C, The bending of the loop of the ventricle is 

 now at the ninth thoracic segment. (From Corning after Duval.) 



II. The development of the heart of the chick. A-E, ventral views of the 

 heart; A, of a forty-hour embryo; B, of a 2.1 mm. embryo; C, of a 3.0 mm. 

 embryo ; D, of a 5.0 mm. embryo ; E, of a 6.5 mm. embryo. F. Frontal section 

 through the heart of a 9 mm. embryo, a, Auricle ; b, bulbus ; d, roots of dorsal 

 aorta ; e, median endothelial cushion ; i, interventricular groove ; la, left auricle ; 

 le, lateral endothelial cushion ; lv, left ventricle ; om, vitelline artery ; p, left pul- 

 monary artery ; ra, right auricle ; rv, right ventricle ; s, interventricular septum, sa, 

 interauricular septum; t, roots of aortic arches; v, ventricle. (A, F, after 

 Hochstetter; B to E after Greil.) 



