8o 



HUMAN EMBRYOS AND FETAL MEMBRANES 



9 and 14 pairs of segments, with three brain vesicles and with the amnion 

 cut away are seen in Figs. 81 and 324. The relation of the fetal appen- 



A mnion 



Body stalk 



FIG. 82. Human embryo of about 2.5 mm. (His, after Coste). X 15. 



dages to the embryo shows well in the embryo of Coste (Fig. 82). The 

 dorsal concavity is probably abnormal. A robust body stalk attaches the 



Amnion 



Branchial grooves 1-3 



Body stalk 



Maxillary process 



Mandibular process 

 Heart 



Yolk-sac 

 FIG. 83. Human embryo of 2.6 mm., showing amnion, yolk stalk and body stalk (His). 



X2 5 . 



embryo to the inner wall of the chorion. With the growth of the head- 

 and tail folds of the embryo, there is an apparent constriction of the yolk 



