PROFESSOR OWEN ON THE AYE-AYE. 59 
The principal muscle of the lower jaw is the masseter, of a quadrate form, one inch 
five lines in breadth by one inch four lines in depth; it arises from the lower margin 
of the zygoma, and from a very strong aponeurosis continued thence over the greater 
part of the outer surface of the muscle. It consists of two portions, an external and an 
internal. The external fibres pass downward almost parallel, to be inserted into the 
lower border of the posterior half of the mandible ; they are separated by a thin glistening 
aponeurosis from the internal portion, the fibres of which pass a little forward as well 
as downward. These two portions blend together anteriorly ; the inner portion is 
inserted into the outer surface of the broad ascending ramus. There is no trace of an 
accessory masseter, such as exists in most Rodents. 
The temporal muscle attains four or five lines in thickness: besides its cranial origin, 
it derives many fibres from the strong temporal fascia, attached to the upper border of 
the zygoma, before passing under the arch to be inserted into the coronoid process. 
The pterygoideus internus arises by a strong narrow tendon from the outer part of the 
base of the spheno-pterygoid ridge, and expands, its fibres diverging, to be inserted into 
the slightly inflected angle and the lower border of the inner depression of the ascending 
ramus of the mandible. The inner or exposed surface of the pterygoideus internus is 
in great part covered by a glistening aponeurosis. 
The pterygoideus externus has a broader and more extended origin; its fibres run 
more parallel, and slightly converge to their insertion into the upper half of the inner 
surface of the ascending mandibular ramus. 
Muscles of the Upper Limb.—The muscles (trapezius and levatores) which attach the 
scapula to the head and neck are large and strong. The latissimus dorsi arises from 
the back part of the last five ribs, and from the broad tendon common to it with the 
sacro-lumbalis and longissimus dorsi: the fibres converge, as they pass over the lower 
part of the scapula, to terminate in the strong flattened tendon (PI. XXIII. fig. 1, »), 
which is inserted into the internal ridge of the proximal third of the humerus. Near 
the beginning of the tendon, on its inner side, is attached the accessory muscle (ib. 224) 
of the long portion (ib.22) of the triceps, by which the influence of the great dorsal 
muscle, most effective in the action of climbing, is extended to the lower end of the 
humerus and the olecranon. 
The teres major (Pl. XXIII. figs. 1 & 2, ») arises from the lower costa of the scapula ; 
its tendon, passing along the upper part of that of the Jatissimus dorsi, is inserted into 
the lesser tuberosity of the humerus. 
The teres minor (ib. fig. 2, ») is not much inferior in size: it arises from the infra- 
spinal space beneath the origin of the scapular spine ; extends forward over the origin 
of the triceps, and under the deltoid, to be inserted into the greater tuberosity. 
The subscapularis, of which a portion is shown in Pl. XXIII. fig. 1, 3, has the 
usual origin from the inner surface of the scapula, by three principal fasciculi, which 
converge to a broad thin tendon, closely attached to the part of the capsule of the 
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