128 ARBOREAL MAN 



in an elongated form from back to front ; it rather becomes 

 rounded, or even broadened from side to side. T hese 

 changes in the bony architecture of the pelvic girdle lead 

 naturally to changes in the disposition of the viscera 

 most intimately related to the pelvis. In particular the 

 splaying open of the hinder end of the symphysis produces 



A B. 



FIG. 46. DIAGRAMMATIC REPRESENTATIONS OF (A) PRIMITIVE 

 MAMMALIAN AND (B) HUMAN TYPE OF VENTRAL SYM- 

 PHYSIS. 



marked alterations in the visceral outlets, since the 

 perineum shares in the changes. The form of the ex- 

 ternal genitalia in both sexes becomes modified by this 

 opening movement of the symphysis; and the external 

 reproductive orifices become situated beneath the pubic 

 arch, instead of occupying the hind end of an elongated 

 pelvic tunnel. The internal organs also become pro- 

 foundly modified, and those channels which connect the 

 hollow viscera with the surface of the body become 

 abbreviated with the outfolding of the hind end of the 

 symphysis. Other visceral changes come about hand in 

 hand with this pelvic adaptation, and this for the reason 

 that both are the results of the altered poise in arboreal 

 activities. As the body axis becomes increasingly 

 upright, the disposition of the viscera within the body 

 cavities imdergoes a purely mechanical alteration. It 

 may be said that the method of packing the organs in 

 the cavities is changed, simply for convenience, as the 



