NO. I TIIK HVI'0TR0CI-IANTI:RIC fossa HRDLICKA 39 



each of these characters. If any part of the gkiteus maximus inserts 

 within the fossa he fore the secondary bone deposits begin, it can only 

 be the weaker fibers or the muscle sheath. But later the fossa is 

 certainly invaded by powerful strands of the muscle, or the weak 

 original strands develop in power. 



The same processes here described occur in all the races and may 

 readily be studied from their inception. But nothing of this nature 

 is found in the anthropoid apes, where, in general, the fossa from 

 the start is seen to serve for a strong muscular insertion and is plainly 

 formed by this insertion. It appears that the conditions in these apes, 

 where the fossa is often of primary, the adjacent gluteal ridge of 

 secondary importance, and the gluteal tuberosity (third trochanter) 

 is absent or moderate, have become reversed in man, where the gluteal 

 ridge and tuberosity have assumed the primary position, and the 

 fossa, though it persists, seems to be a sort of left-over, of only secon- 

 dary significance. These observation^i^would not hold good, however, 

 if the human fossa during the growth period should be found to 

 exercise some special function. It is tantalizing that, with all these 

 fine skeletal series now at our command, the last point cannot be 

 settled for the want of suitable dissection materials. 



A few additional observations may be recorded. 



In examining the adult femora it seemed in some bones that the 

 fossa may have regressed, both in depth and size, even without any 

 discernible secondary bone formation. This would imply interstitial 

 growth of bone underneath and about the fossa. 



The oblong or rounded gluteal tuberosity (third trochanter) was 

 seen in some bones to be located completely above and well separated 

 from the fossa, not affecting this in any way ; or to involve its upper 

 end; or to be lying sometimes completely within the hollow. In one 

 femur the tuberosity was situated as low down as the middle of the 

 fossa ; in none was it below the middle. In not a few adult specimens a 

 large tuberosity (third trochanter) alone so filled the fossa that only a 

 bare trace of it, perhaps only a part of its old outline, remained 

 perceptible. The tuberosity, when it is in the fossa, may be said to 

 have an even greater effect on the regression or disappearance of 

 the hollow than the gluteal ridge ; but as the tuberosity in many cases 

 is a constituent part of the ridge, exact statements are difficult in this 

 connection. 



The matter of the relation of the gluteal ridge to the gluteal tuber- 

 osity and the fossa will be dealt with further in another paper. The 

 main points that may succinctly be repeated are that in man, from 

 later childhood onward, the fossa in increasing numbers of cases 



