182 THE GENERAL ANATOMY OF GORILLA [SECT. A 



reminiscent of those found in the Cercopitheci, though departures 

 in the direction of the characteristic human disposition of these 

 muscles are numerous. On the whole, however, distinct evidence 

 of affinity with the lower forms persists. And this indicates that 

 the predominant use of the fore-limb in climbing has been effective 

 in securing the retention of the appropriate arrangement. 



The osseous origin of the M. latissimus dorsi is of particular 

 interest, in view of the relation of this muscle to movements in- 

 volved by an arboreal mode of existence ; the muscle arises from 

 the tenth and succeeding vertebral spines, and in its attachment 

 to the crista ilii is found to be much more extensive than in Man, 

 for it arises along the whole length of this bony crest (in the 

 Chimpanzee it may even encroach upon the region of Poupart's 

 ligament). The tendon of insertion has relations with that of M. teres 

 major similar to those described in the Cercopithecidae (v. supra). 



The M. dorsi-epitrochlearis needs no special description, but its 

 retention would appear to be determined by that of the use of the 

 limb for climbing. The chief characteristic of the M. teres major 

 is the occasional great breadth of its scapular attachment. 



The M. pectoralis major closely resembles that of Man. The 

 lowest fibres usually constitute an independent muscle, the " pars 

 abdominalis 1 ." The insertion of the M. pectoralis major is some- 

 times carried to the tendon of the M. coraco-brachialis. The M. 

 pectoralis minor (Fig. 121) also resembles its counterpart in Man, 

 though its costal attachment is more extensive (as far as the 

 seventh rib in some cases) and it is subdivided by the great 

 laryngeal sac which perforates it and protrudes in the axilla. On 

 the whole however the muscles of the pectoral region approach 

 more nearly the human condition than do those of the nuchal 

 and dorsal regions. 



5. The M. coraco-brachialis is frequently double 2 , and consists 

 then of a long and a short portion. The muscle may be found 

 conjoined with (a) M. latissimus dorsi, (b) M. triceps or (c) M. 



1 Windle, " The Pectoral Group of Muscles," Trans. Roy. Irish Acad. Vol. xxix. 

 part xii. This muscle, arising from the aponeurosis of the M. obliquus externus, is 

 sometimes termed M. pectoralis quartus. In Man, it blends with the costal portion 

 of the M. pectoralis major. 



2 It is however single in the adult Gorilla (Cy) dissected by the writer at 

 Cambridge. 



