AND GENERATIVE ORGANS IN THE MALE CHIMPANZEE. 1007 



Muscles of the Perineum and Pelvis (text-figs. 63 and G4). 



"When the skin is removed from the perineum the suhjacent 

 fa,scire are seen to consist of an imperfect supei'ficial fatty stratum 

 and a deep fibx'ous layer, which is not connected to the triangular 

 ligament. 



The sphincter ani externals (text-tig. 03) is a powerful muscle, 

 and there is continuity between it and the levator ani. It con- 

 sists of several parts, most of Avhich foi'm collars round the gut. 

 The superficial part (S.A.S.) arises in front from the triangular 



Text-figure G3. 

 u 



The pelvic muscles. A.C.ll: auo-coccj-geal raphe ; C.P.P : central point 

 of perineum. Other letters in text. 



ligament in the central point of the perineum ; they sweep round 

 the anus, but they have no fixed posterior attachment. Two long 

 muscle bands (S.A.E.) arise from the inner aspects of the posterior 

 parts of the ischial tuberosities and meet behind the anus; some 

 of the fi.bres are continuous with those of the superficial part of 

 the sphincter. The com])lete band appears like a sling. It is not 

 present in all Chimpanzees, and it may correspond to the retractor 

 ani of lower Mammals. The third part of the muscle (S.A.T.) is 

 composed of fibres arising from tiio central point of the perineum 

 and sweeping round the gut ; it forms a. thick collar above and 



