NO. I 



THE HYPOTROCHANTERIC FOSSA HRDLICKA 



37 



The above data are striking enough, but they will l)e even more so 

 if we condense them thus : 



Hypotrochanteric Fossa in Adolescents and in Adults Compared, Both Sexes, 

 Both Sides (Condensed) 



Group 



U. S. Whites: 

 Adolescent . 

 Adult 



None 



Percent 



15 4 



32- 



Trace 



to 

 small 



Submedium 



to 



medium 



Above 

 medium to 

 pronounced 



U. S. Negroes: i 



Adolescent (3 1 • - 1 



Adult 1 3' - 



Old Egy^ptians: 

 Adolescent . 

 Adult 



Old Peruvians: 



Adolescent . 

 Adult 



X. A. Indians: 

 Adolescent 

 Adult 



Eskimos: 



Adolescent 

 Adult 



2.9 

 20.5 



6.3 



24.4 



2.9 

 12.2 



3 - 

 10.4 



Percent 

 30.8 

 38.2 



23- 



39 



14 3 



37-5 



II 



50 



8.6 

 51 7 



13 I 

 42.8 



Percent 

 46.1 

 27- 



35- 

 28. 



42.9 

 35 - 



44 3 

 24.2 



53 4 

 34 - 



53-5 

 41.8 



General approximate means: 



Adolescent" 



Adult 



6 

 21 . 



16.9 

 43-2 



45 9 

 31 7 



Percent 

 7.6 

 2.8 



II . 



2. 



40.- 



7 ■~ 



38.- 

 I . I 



35 I 



30. 

 5 



27 - 

 3 3 



" Omitting the Negroes. 

 ' With the Negroes — 10.2. 



The above figures mean that in advancing through the adult life 

 the human femur loses a large proportion of the more marked grades 

 of the hypotrochanteric fossa, gains largely in the " trace " to " small " 

 grades, and to a considerable degree loses the fossa entirely. 



This is a highly interesting and, in its definiteness, so far a unique 

 phenomenon in anatomy and anthropolog}'. It is known, of course, 

 though only very generally, that structural changes proceed in prob- 

 ably all parts of the body as age advances, but there is as yet no 

 parallel to such a peculiar and clear-cut range of manifestations as 

 offered by the hypotrochanteric fossa. Here is a formation of some 

 note which, it has been seen, advances steadily in both its incidence 

 and its development during a very large part of the growing period 

 but which, once the adult life is reached, enters upon a retrogressive 

 path tending toward its disappearance. 



The strange phenomenon presents two problems. The first of these 

 is, what causes the long sustained development of the fossa during 



