SKELETON OF QUADRUMANA. 547 



The clavicle, 58, is thicker than that in Man, with a subtrihedral 

 shaft and the sigmoid flexure less marked ; the sternal articular sur- 

 face is less oblong ; the acromial end is broader and flatter below. 



The humerus, 53, though surpassing iii length that of Man, 

 fig. 183, 53, is thicker and stronger in all its ridges and processes ; 

 especially at the lower extremity, the transverse diameter of 

 which surpasses that of the upper extremity of the bone in a 

 greater degree than in Man : both tuberosities are relatively 

 greater, the ' lesser ' one more especially. Immediately above 

 the distal articular surface are two depressions divided by a ridge 

 continued to the prominence between the radial and ulnar arti- 

 culations ; the outer or radial depression is the smaller and shal- 

 lower, the inner or ulnar one is larger : it answers to the 

 * coronoid fossa ' in Man, but becomes a foramen in full-grown 

 Gorillas, by absorption of the thin plate of bone dividing it from 

 the anconeal fossa behind. The ectocondyloid prominence is 

 more marked than in Man : the entocondyloid one is more pro- 

 duced, is angular, and compressed. The back part of the humerus 

 shows, as in Man, the musculo-spiral tract dividing the ridges 

 for the external and internal heads of the ' triceps extensor.' 

 The configuration of the lower articular surface is closely similar 

 to that in Man ; the whole surface extends a little further below 

 the condyloid prominences, allowing to that extent a more free 

 sweep of the fore-arm in flexion and extension, and adding power 

 to the leverage of the tendons inserted into the antibrachial bones. 



The medullary artery enters the fore part of the shaft, but 

 nearer the middle of the bone in the Gorilla than in Man : in 

 both the course of the canal is towards the elbow-joint. The 

 head of the radius, 54, has an elliptical contour : the shaft bends 

 outward so as to leave a wider interosseous space than in Man. 

 The neck expands to the tuberosity wdiich shows an oblong rough 

 prominence for the insertion of the tendon of the biceps, behind 

 or ' ulnad ' of the smoother prominence supporting the bursa 

 interposed between it and the tendon. Below the tuberosity the 

 shaft assumes a pyriform transverse section through the develope- 

 ment of the interosseous rido^e, which extends to near the * sis:- 

 moid cavity.' The styloid process is represented by a prominence 

 which gives a larger surface than in Man for the insertion of the 

 tendon of the ^ supinator longus.' It is not impressed, behind or 

 externally, so deeply by the two grooves for the extensor muscles 

 of the metacarpal and first phalangeal bones of the thumb : a still 

 stronger tuberosity divides the fossa for the radial extensors of 

 the wrist, from the Avider and deeper one for the strong tendons 



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