550 ANATOMY OF VERTEBRATES. 



than the outer one, as in Man. The rotular surface is shallower, 

 the lateral borders are better defined : the medullary artery enters 

 the middle of the back part of the shaft, and the course of the 

 canal is proximad or upward. 



The length of the tibia is one foot six lines, and its shaft is 

 as thick as in Man, and expands more gradually to the distal end : 

 the conformation of the proximal surface is similar to that in Man ; 

 the spine is rather stronger, and an anterior spine or tuberosity is 

 more distinctly developed. The internal tuberosity in front of the 

 fibular one is better defined ; the interosseous ridge is very feebly 

 marked in the Gorilla, and the anterior ridge of the shaft is much 

 less marked than in Man, The astragal ar surface is more undu- 

 lating, less concave, and more directly continued upon the internal 

 malleolus : the side of the distal end next the fibula, instead of 

 being concave, forms an angular projection. The fibula is stronger 

 in proportion to its length than in Man; the lower articular 

 surface of the fibula is flatter, and divided into tAvo facets more 

 distinctly, than in Man. 



The astragalus of the Gorilla equals in size that of Man, 

 but is broader in proportion to its length: the surface for the 

 tibia is less defined, especially from the inner facet, which in the 

 Gorilla is almost horizontal and appears as a concave inner termi- 

 nation of the upper surface. The anterior surface is more convex, 

 especially vertically, and more directly continued into the anterior 

 calcaneal surface. The inner tuberosity is larger and more ad- 

 vanced : the Gorilla differs from the Chimpanzee in the greater 

 size of this process, and in the greater proportional size of the 

 scajohoid convexity, in which respect its astragalus more resembles 

 that of Man. The calcaneum of the Gorilla is a lonirer and more 

 slender bone than in Man, which is chiefly due to the greater 

 length and slenderness of the posterior or calcaneal process. The 

 lower surface of the bone is smoother, narrower, and more concave 

 longitudinally : the groove for the flexor tendons beneath the inner 

 astragalar surface is wider and better defined: that astragalar 

 surface is broader in proportion to its length, and there is a deep 

 longitudinal groove on the outer side below the outer astragalar 

 surface, which does not exist in Man. The anterior cuboidal sur- 

 face is placed further from the outer side of the bone than in 

 Man ; the outer side forming a rough convex protuberance at its 

 anterior half. The naviculare is one third larger than in Man, the 

 increase being in its transverse extent, and due to the greater 

 development of the rough convex protuberance at the inner end of 

 the bone. The entocuneiform has an equal vertical, but a minor 



