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, Pl. 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 
abruptiy 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 (0), 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 (0) 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 issmaller and deeper. The smooth 
triangular surface near the origin of the spine (s), upon which the trapezius muscle glides, 
is relatively greater. The surface (¢) 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 magnus 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 
