24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



more couinioii and more developed ; the hypotrochanteric fossa is as a 

 rule relatively high on the shaft and is hollowed in the lateral part 

 of the posterior surface, rarely approaching, and never embedded 

 in, the lateral border of the bone. And there are other dilTerences, 

 which will be brought out in our detailed studies. All of this implies 

 that there must exist, between man and the rest of the prmmtes, 

 important differences in muscular attachments and in other soft parts 

 of the region in question. In comparing the features of this region 

 in man with those of the other primates, we are comparing, therefore, 

 what basically are homologous formations, but formations that in 

 their ultimate development in man and the other genera are no longer 

 necessarily fully equivalent morphologically or functionally. The 

 hypotrochanteric fossa, which is here more especially considered, al- 

 though present and even frequent in man, may thus be in him an 

 " emerited " survival, a still frequent but no longer functionally im- 

 portant memento of his past, rather than a still fully active cog of his 

 mechanism. 



It may be useful to bear these reflections in mind when confronted 

 with some of the curious results of this study. 



THE FOSSA BEFORE AND ABOUT TIME OF BIRTH 



Material Examined 



Femora 



U.S. Whites (miscellaneous) 161 



U.S. Negroes (fullbloocl and mixed-blood) 262 



The first traces of the fossa may be discerned occasionally as early 

 as the fifth month of the intrauterine life; their detection is made 

 easier by the use of a magnifying glass of medium power. Its first 

 plain representation is a well-demarked, not depressed, evenly reticu- 

 lated roughness. As the age of the bones advances, this area assumes 

 slowly the character of a hollow, and the reticulation of its floor 

 diminishes until, in a fully formed fossa, the floor is generally fairly 

 smooth and uniform. 



The formation of the first distinct stages of the fossa is mostly 

 associated with the appearance on its mesial border of the first traces 

 of the gluteal ridge, but the fossa may antedate the ridge, or it may 

 begin to develop later. We shall return to this discussion. 



