PHYSIOLOGY, AND PATHOLOGY OF THE CHIMPANZEE. 363 



of the same toe. The third is placed more superficially than 

 the others, and lies in the same plane as the opponens minimi 

 digiti. Its belly crosses the fourth space from its origin on the 

 external long plantar metatarsal ligament, and the ligaments 

 over the base of the fourth metatarsal to its insertion on the 

 inner side of the fifth toe. 



The dorsal interossei are inserted more into the proximal 

 phalanx than into the dorsal expansion, but the plantar inter- 

 ossei exhibit the reverse. 



The important points to be noted from the physiological point 

 of view are : — 1. The middle line of the foot runs through the 

 middle toe instead of through the second, as in Man. So the 

 interossei of the foot of the Chimpanzee act as they do in a hand. 

 2. There are no additional plantar interossei in the foot as there 

 are in the hand. 



The disposition of the muscles in four layers in the sole of the 

 foot is as in Man. 



The nature of the terminal part of the pelvic extremity is 

 described on page 423. 



Muscles of the Pelvis. 



Levator Ani: — In this animal the levator ani consisted of the 

 same parts as described by Lartschneider (32). The iliac portion 

 arose from the margin of pelvis minor, and the pubic portion 

 arose from the back of the symphysis pubis. It is inserted into 

 the sides of the lower end of the rectum and the ano-coccygeal 

 raphe. 



The ischio-coccygeus is a small muscle running from the side of 

 the coccygeal vertebi-se to the inner aspect of the back part of the 

 ischial tuberosity. 



Lartschneider has described a pelvic diaphragm in a female 

 Chimpanzee. 



The perineal micscles diflTer from those in the human condition. 

 The vulva and anus are very close together, so there is no true 

 centi'al point of the perineum, nor is there a trace of transverse 

 perineal muscles. The ischio-cavernosi have long origins from 

 the ascending pubic rami ; they run over the crura clitoi-idis, and 

 the opposite muscles are blended. The s2yhinGter vagince is a 

 strong collar surrounding the upper part of the vagina and 

 extending backwards on to the rectum. It has a narrow anterior 

 slip which fuses with the meeting point of the two ischio- 

 cavernosi. The sjyhincter ani externus blends in front with the 

 sphincter vaginae, and it is attached behind to the ano-coccygeal 

 raphe, which is very powerful. 



The ischio-rectal fosste are well marked and laden with fat. 

 No well-marked bursa exists over the ischial tuberosities. And 

 the fascia is not divided as in Man into a superficial fatty layer 

 and a deep fascia of Colles. 



The orbital muscles are described on page 415, and the laryn- 

 geal muscles on page 398. 



