THE CHIMPANZEES AND ORANGS. 3 



facet near the base for the attachment of a strong ligament ; the inner surface of the 

 coracoid presents a deep and well-defined depression, beyond which it is convex. 



The scapula of the Chimpanzee {Troglodytes niger, PI. I. figs. 4, 5, 6) departs, 

 like that of the Gorilla, from the Human type in the more equal division of the outer 

 surface of the bone by the spine ; but it approaches still nearer to the form of the blade- 

 bone in the lower Quadrumana by its narrowness in proportion to the length. The 

 superspinal tract is even and almost flat, or very slightly convex, the spine arising more 

 abruptly from it. The subspinal tract is less undulated than in the Gorilla, and a 

 greater proportion of it is concave. The upper border, convex outwardly by the curving 

 in of the basal border (o), seems to have its concave part formed wholly by the wide 

 superscapular notch. The basal border makes a slight concavity at the origin of the 

 spine, but its convex curves are less marked than in the Gorilla. The lower border is 

 straight, with a less extent of surface for the teres major than in the Gorilla. The inner 

 surface of the scapula is relatively deeper than in the Gorilla, with only three short 

 ridges at its lower half close to the basal border, for the attachment of the tendinous 

 intersections of the subscapularis muscle, and with the straight ridge extending from 

 near the inferior angle to the neck of the scapula, and defining, with the inferior border, 

 the longitudinal channel for the teres minor. The glenoid cavity (fig. 5, g) is narrower 

 in proportion to its length than in the Gorilla or in Man, but has a thinner border, 

 except at the upper end, than in the Gorilla. 



The spine of the scapula ascends more obliquely, and forms a more acute angle with 

 the lower border of the bone than in the Gorilla, thus departing further from the Human 

 type ; the acromion is narrower in proportion to its length. The coracoid (fig. 6, c) is 

 relatively less expanded and flattened externally, and consequently resembles more in 

 shape that of Man (fig. 7, c) ; but the ridge for the trapezoid ligament is more marked. 



The peculiarities of the Human scapula (PI. I. figs. 7 & 8), as brought out by these 



comparisons, are the great breadth in proportion to the length, the more transverse 



direction of the spine and acromion, and the disproportionate extent of the subspinal 



as compared with the supraspinal tract. The upper angle (o) is less rounded; the 



extent of the upper border between that angle and the superscapular notch is relatively 



greater, and is more nearly straight ; the notch itself is smaller and deeper. The smooth 



triangular surface near the origin of the spine (s), upon which the trapezius muscle glides, 



is relatively greater. The surface {t) for the teres minor muscle on the outer side of the 



bone near the lower border, is broader ; as is that for the teres major, nearer the lower 



angle. The deep part of the subscapular bed, being parallel with the attachment of 



the spine of the scapula, is situated nearer the upper border than in the Gorilla or 



Chimpanzee. The surface for the upper origin of the serratus raagnus is relatively less 



than in the Gorilla. The long narrow surface between the obtuse lower boundary of the 



subscapular fossa and the lower border of the scapula is flat, or is less concave than in 



either the Gorilla or Chimpanzee. 



b2 



