THE BONES 



73 



there are tailless animals in other orders, and the backward 

 curve of the coccygeal vertebras (named by Waldeyer " inner 

 tail " or cauda occultd) is shared by the tailless anthropoids. 

 Embryological research has proved that the early progenitors 

 of man, and the anthropoids, undoubtedly had outer tails. 

 The human embryo of from four to six cm. has a real tail 

 outwardly visible and projecting, with segments, medullary 

 canal and caudal intestine. 1 The spot where the point of the os 



Sacrum 



Acetabulum 

 Suture of the pubic bone 



Cavity of the hij 



Hip-bone 

 FIG. 32. Male pelvis. (Ranke, D. M.) 



Sacrum 



Iliac bone 



Ligament 

 Coccyx 



Hip-bone jmif ^^gpr^ Suture of pubic bone 



FIG. 33. Female pelvis. (Ranke, D. M.) 



coccygis presses outwards against the skin, where formerly the 

 tail actually passed through before the subsequent curving of 

 the sacrum, is indicated in the embryo by the vertex coccygeus. 

 As the time of birth approaches, this vertebra disappears 

 and is replaced by a smooth hairless spot (glabella coccygea) 

 which often assumes the form of a small depression (foveola 

 coccygea). 2 



1 Wiedersheim, loc. cit., p. 27. 2 Ibid., p. 7. 



