NO. I THE HYPOTROCHANTERIC FOSSA HRDLICKA 45 



It is obvious that in some femora the hypotrochanteric fossa is 

 no neghgible feature. 



LIFE HISTORY OF THE FOSSA 



Thanks to the data it has been possible to present here, it is prac- 

 ticable, for the first time, it seems, in anatomy and anthropology, to 

 view — grossly at least — the whole ontogeny, the full life history, of 

 a definite feature of human morphology. 



The life history of the hypotrochanteric fossa could be presented 

 graphically in the form of a curve of long but steady ascension, a 

 mildly rounded or flat summit, and then a prolonged descent to about 

 or even below one half of the height of the earlier rise. In other 

 words, we see first a gradual long rise of the fossa on a phylogenetic 

 basis toward the condition of a fuUfledged character, and then its 

 slow, irresistible assimilation by a vigorous neighboring feature. 



And there are indications — in some instances, or to some degree, 

 definite proofs — that every single separate organ or part of the human 

 body, and every human function, too, has its own extensive and highly 

 interesting life history, a history connected in its origins with human 

 derivations and antiquity, and ending in advancing regression and 

 apparent preparation for disappearance; or in seeming tranquility, 

 stability ; or in some degree of progressiveness toward a greater repre- 

 sentation. The realization of these conditions opens a vast and in- 

 tensely attractive field for coming researches. The studies of human 

 variation and those of the life histories — or perhaps they should 

 be called existence histories — of the innumerable components of 

 human structure and functions are the most alluring realms of human 

 anatomy, physiology, and anthropology of the future. 



THE FOSSA IN LOWER MAMMALS 



Thanks to the aid of the division of mammals of the United States 

 National Museum, I have been able to examine for the fossa a series 

 of femora representing the principal mammalian forms, with the 

 following results : 



Carnivores : 



Lion No hypotrochanteric fossa 



Tiger 



Puma 



Wolf 



Fox 



Bear 



