26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



of specimens become more adequate, the conditions in the two groups 

 are seen to be closely alike. About and for a brief time after birth 

 ( femur length 7 to 8.95 cm) the relations are as follows: 



The differences are still small but apparently significant. In the 

 white femora the fossa shows throughout a slight advantage. At and 

 shortly after birth the fossa may therefore be said to tend to be sHghtly 

 more frequent and more commonly slightly better developed in the 

 U. S. White than it is in the U. S. Negro. 



The main point, however, shown by the above records is the gradual 

 appearance and growth of the fossa during those early stages. As the 

 age of the fetus and later that of the infant advances, the fossa be- 

 comes steadily more frequent and more substantial. In view of these 

 data it is evident that the formation of the hypotrochanteric fossa, 

 initiated in rare instances as early as the fifth month of intrauterine 

 life, begins in different femora at different periods before and even 

 after birth. 



THE FOSSA IN CHILDREN, ADOLESCENTS, AND SUBADULTS 



The available juvenile femora, although collectively considerable in 

 number, when divided into the more obvious ontogenetic periods are 

 still not always sufficient for our purposes. The inadequacy applies 

 particularly to the bones of the children and adolescents of Whites, 

 which are scarce in all our collections. On the other hand, however, 

 there are excellent series from racial groups that were not represented 

 in the fetal material, and altogether there is enough to bring out the 

 most salient facts about the feature under scrutiny. 



The subdivisions to be used are: i. The earlier childhood (up to 

 approximately 6 years of age) ; 2, later childhood (approximately 

 7 to 13 years) and earlier adolescence (both upper and lower 

 epiphyses still detached) ; 3, later adolescence (lower epiphyses alone 

 detached); and 4, subadult (approximately 19 to 21 years; all 

 epiphyses attached but lower still imperfectly so or but recently). 



