

MUSCULAR SYSTEM OF MAMMALIA. 53 



From the Aye-aye to the Gorilla, 1 with a few exceptions, there 

 is a * cleido-mastoideus ' as well as a ' sterno-cleido-mastoideus ; ' 

 but in some Baboons (Macacus) the distinct fasciculus from the 

 clavicle has not been found. In an Orang I found the cleidal 

 part inserted into the diapophysis of the axis vertebra. 



The term ( digastricus ' is applicable to that mandibular muscle 

 in all Quadrumana, although the partition by tendon of the ante- 

 rior from the posterior belly is not complete in many. In most, 

 as in the Aye-aye, the anterior portions of the pair occupy the 

 anterior interspace of the mandibular rami. The middle tendi- 

 nous part is attached to the hyoid, except where it is feebly 

 marked, as in Stenops. The intermediate tendon of the omohyoid 

 is not found save in the higher tail-less Apes. 



In all Quadrumana the power of the arms in drawing up the 

 trunk is increased by the accessory muscle from the ordinary ten- 

 don of the ' latissimus dorsi,' which extends its action from the 

 upper to the lower end of the humerus (interior condyle), and to 

 the olecranon. The ' rhomboidei ' extend to the occiput in Maca- 

 ques, Baboons, and the Orang. The 'protractor scapulae' (' acro- 

 mio-trachelien,' Cuv.) exists in most Quadrumana below the Apes; 

 in these the ( levator anguli scapulae ' is distinct from the ' serratus 

 magnus ; but is the fore part of that muscle in Baboons.' In the 

 Gibbons (Hylobates) the two portions of the 'biceps flexor cubiti' 

 are more powerful and unite lower down the lumerus than in other 

 Quadrumana, and the inner portion derives an origin from near 

 the pectoral ridge of the humerus : their common tendon is inserted 

 beneath the radial tubercle, and into the antibrachial fascia. In 

 Stenops the biceps has only its 'long head' or origin : that from the 

 coracoid process is, at least, not distinct from the coraco-brachialis. 

 The ' triceps extensor cubiti ' is complicated in Quadrumana 

 by the accessory fasciculus in connection with the tendon of the 

 latissimus dorsi. The lower portion of the ' internal head ' of the 

 triceps has also a distinct origin or fasciculus from the ento- 

 condyloid ridge in Chiromys and Tarsius ; in Stenops it arises 

 more from the back part of the humerus. 



The deep and superficial flexors of the fingers are distinct, but 

 a remnant of that blending which exists in most lower mammals 

 may be seen in the short connecting tendon which in the Aye-aye 2 

 passes from the ulnar belly of the ' flexor sublimis ' to the division 

 of the ' flexor profundus,' giving off the tendon to the middle finger. 

 The fleshy part of both flexors, but especially of the deeper one, 

 is continued nearer to the hand, in Lemurida and most other 

 1 cn\ p. 30, pi. xi. fig. 1, 22 d. 2 cir. p. 34, pi. xi. fig. 4, e. 



