EXISTING ORGANISMS— EMBRYOLOGY 



63 



A trium 



{behind ventricle) 



trial 

 canal 



Ventricle 



D 



Intervent. 

 I sulcus 



Ventricle 



Fig. 42. — External form of the human heart during development. A, from 

 an embryo of 2.15 mm; B, 3 mm; C, 4.3 mm; D, 10 mm. (From Arey's 

 Developmental Anatomy, after His, with the permission of the W. B. Saun- 

 ders Company.) 



