PROFESSOR OWEN ON THE AYE-AYE. 59 



The priacipal 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 margm 

 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 shghtly 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 fibi-es 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 Limh . — The muscles {trapezius s.nA 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, le), 

 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 (i6.22"i) 

 of the long portion (i&.22o) 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 (PI. XXIII. figs. 1 &2, 12) arises from the lower costa of the scapula ; 

 its tendon, passing along the upper part of that of the latissimus dorsi, is inserted into 

 the lesser tuberosity of the humerus. 



The teres minor {ib. fig. 2, 10) 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 suhscapularis, of which a portion is shown in PI. XXIII. fig. 1, 13, 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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