AND GENEKATIVE OUGANS IN TUE MALE CHIMPANZEE. 1009 



the crura, bxilb, niul io-iaiujular ligament are exposed. The liga- 

 ment is strong and composed of two layers, which meet behind 

 and are turned up over the posterior part of the bulbo-cavernosus 

 muscles. The terminal part of the pudendal aiteiy turns up over 

 the recurved base (text-lig. (53, P.A.). The bulb of the corpus 

 spongiosum is attached to the perineal surface of the ligament. 

 VVHien the suporticial layer is removed the two large Cowper's 

 glands are seen lying in pockets at the sides of and above the 

 bulb. The glands shine through the superlicial part of the 

 ligament. 



The comj)ressor urethrce encircles the urethra between the layers 

 of the triangular ligament. 



Between the anal canal and the obturator internus there lies on 

 each side a narrow, deep ischio-rectal fossa. And the pudendal 

 arteiy, after emerging from under cover of the great sacro-sciatic 

 ligament, passes along under the fascia at the meeting of the outer 

 and inner walls of the space. The vessel turns up over the trian- 

 gular ligament and ends by supplying the crura, bulb, Cowper's 

 glands, and the skin of the perineum (text-fig. 63, P.A.). Within 

 the space it gives off the inferior luemorrhoidal arteiy to the 

 sphincter and levator ani (text-fig. 63, I..H.A.). 



The ischio-rectal fossa has the same boundaries as in Man, and 

 the fascipe covering its walls are likewise similar. Alcock's canal 

 is, however, poorer. 



The levcdor ani (text-figs. 63, 64, L.A.) is covered on both sur- 

 faces by fasciae as in Man. The inferior fascia is delicate and 

 continuous with the equally delicate fascia over the obturator 

 internus. The muscle arises from the back of the body of the 

 pubis, the margin and inner wall of the true pelvis and the place 

 where the ischial spine lies in Man. The fibres pass downwards 

 and inwards to be inserted into the central point of the perineum, 

 the sides of the anal canal, the sphincter ani externus, the ano- 

 coccygeal fascia, and the lower sacral and coccygeal vertebras. 

 The anterior two- thirds of the muscle are thick and powerful, but 

 the posterior third is thin. 



The coccj/(/ens has similar attachments and relations to those 

 in Man. 



Conclusions. 



A. The external generative organs in Man difier from those of 

 the Chimpanzee in the following particulars : — 



1. The glans penis is well marked. 



2. There is no os penis. 



3. The corpus spongiosum lies in a groove on the ventral 

 surface of the fused corpora, cavernosa. 



4. The septum between the corpora cavernosa persists longer. 



5. Tlie connective-tissue walls of the corpora, cavernosa are 

 not so thick and they have more erectile tissue. 



Man also differs from the Orang in the above features. The 

 chief difterence between him and the Gorilla lies in the absence 

 of the, OS penis. 



