EARLY HUMAN EMBRYOS AND THEIR MEMBRANES 



77 



toderm has invaded the mesoderm of the body stalk. This embryo, 

 seen from the dorsal side with the amnion cut away, shows a marked neural 



Neural groove'^ .. / 



Neurenteric canal 



Primitive streak 



Body stalk 



Villi of chorion 



Amnion 

 Embryonic disc 



A nlage of heart 



Splanchnic mesoderm 



'horion 

 Somatic mesoderm 



Body stalk 

 Primitive streak 



Blood vessel 



FIG. 77. Views of a human embryo of 1.54 mm. (von Spee). X 23. A, Dorsal surface; B, 

 median sagittal section. 



groove and primitive streak. In front of the primitive knot a pore is 

 figured, leading from the neural groove into the primitive intestinal 



