PHYSIOLOGY, AND PATHOLOGY OF THE CHIMPANZEE. 371 



border of the foot ; (2) the talus and calcaneus are more for pro- 

 gression than support; (3) the calcaneus easily rolls outwards on 

 its lower surface, so does not act as a bearing surface ; (4) the 

 calcaneus is thrown out of the plane of gravity, and it is reduced 

 like its homotype, the pisiform, to a lever for muscles ; (5) the 

 talus, navicular, and calcaneo-navicular ligament transmit weight ; 

 (6) the posterior surface of the talus slopes downw ards and in- 

 wards ; (7) the action of the calf -muscles on the foot is unfavour- 

 able for lifting weight or propelling the body; (8) there is no 

 plantar arch, so the navicular bone with the calcaneo-navicular 

 ligament rest on the ground and do not transmit weight along 

 the arch to the hallux, which is not adapted for support ; (9) the 

 mobility of the hallux is obtained by articular, osseous, and 

 muscular arrangements similar to those of the human pollex ; 

 (10) there is more power of flexing the digits towards the sole 

 than in Man. 



It is, therefore, evident that the joints of the neck, pelvis, 

 wrist, nnd lower extremity, particularly the latter, differ con- 

 siderably from those in Man, and all are specialisations in 

 accordance with the mode of locomotion. 



The Organs of Digestion. 



The loose, thick, fleshy lips are projected forwards over the 

 maxillae. No philtrum is present, and in the living animal only 

 a small part of the red margin of the lower lip is visible when 

 the mouth is closed. Their inner surfaces are studded with the 

 openings of numerous labial salivary glands. The labial frenula 

 are long and narrow. The gape of the mouth is wide. The 

 cheeks are loose and mobile, but no pouches exist. The vestibule 

 is semilunar, and receives the secretions of Stensen's ducts, which 

 open on papillae placed as in Man. And a row of papillae lies 

 beside the salivary papilla on each side (text-fig. 28 C). Rex (41) 

 has described the histology of the lips, and Ehlers (59) described 

 folds of mucous membrane connecting the gums and cheeks. The 

 cavum oris is thrice as long as broad according to Gratiolet (22). 

 In my specimen the measurements are: — 



Length of hard palate 2*7 inches. 



Length of soft palate ]•! „ Total = 3-8 inches. 



Greatest width of palate .. . 1*4 „ 



Much, however, depends on the age of the animal. Keith has 

 shown that the breadth of the palate is greater than the length 

 in new-born animals. The cavity of the mouth has also been 

 mentioned by Symington (48) and Tyson (60). 



The rugte of the hard palate have been figured or described by 

 Beddard (3), Bischofi'(60), Ehlers (59), Gratiolet (22), Symington 

 (48), and Waldeyer (52). In my specimen there are no complete 

 ridges crossing the palate, and no incisive papilla. Eleven pairs 



