THE ANATOMY OF A 4.2 MM. HUMAN EMBRYO 



95 



(4) to the development of the extremities and disappearance of the tail. The 

 more important of these changes will be dealt with in later chapters. 



Fig. 86. — Embryos of the second month from His' Xormentafel (Keibel and Elze). 



Age of Human Embryos. — The ages of the human embryos which have 

 been obtained and described can not be determined with certainty, because fer- 

 tilization does not necessarily follow directly after coitus. It has been shown 



