154 



TEXT-BOOK OF EMBRYOLOGY. 



can be expressed fairly accurately by the square root of the length multiplied by 

 100 (Jlength in mm. x 100). In embryos between 100 and 220 mm. the age 

 in days is about the same as the length in millimeters. 



Some of the most important embryos which have been described are 

 listed in the accompanying table, no pretense being made of giving a complete 

 list. The table is compiled largely from the more extensive tables of Mall 

 and merely serves to indicate some of the younger embryos with fairly well- 

 known histories, from which certain conclusions have been drawn concerning 

 the relation of age to length. The periodicals in which descriptions may be 

 found are given with the authors' names in " References for Further Study" 

 at the end of this chapter. 



Normal, Abnormal and Pathological Embryos. 



In the majority of cases of spontaneous abortion it is not possible to examine 

 the uterus; but in those cases where it is possible, examination frequently shows 

 abnormal or pathological conditions. As might be expected, the embryos 

 obtained from abnormal or pathological uteri very frequently show anom- 

 alous conditions or pathological changes, or both. Since many of the 



