Anatomy of the drill. 



433 



aiifl it is inserted into the vertebral border and margin of the 

 deep surface of the scapula. It is impossible to separate it into 

 major and minor rhomboids. The sheet does not extend to the 

 occiput as it does in many Piimates. 



The serratus magnus arises from the first ten ribs and inter- 

 spaces, but the origin forms a uniform muscular line instead of 

 pointed slips as in Man. Its insertion into the A'ertebral border 

 of the scapula is thick and muscular. 



The omo-trachelian is a powerful mnscle attached to the supra- 

 spinous fossa and root of the spine of the scapula. 



The dorso-ejntrochlearis (text-fig. 11, J) is a very strong muscle. 

 It is 4| inches long and 1| broad. Proximally it is intimately 

 connected to the latissimus dorsi and teres major. Its rounded 

 distal border is bound by a strong tendon to the internal condyle 

 of the humerus and the olecranon. It is supplied by a branch of 

 the musculo-spiral nerve (text-fig. 23, D.E.M). 



Text-figure 11. 



The structures in the axilla and arm. A and C : short and long heads of biceps ; 

 B : coraco-brachialis ; D : fascia ; E : pectoralis major ; F.G : axelbogen ; J.K : 

 dorso-epitrochlearis ; L : internal condyle ; M : olecranon ; N.O.P : axillary 

 vessels and nerves ; R.S : long subscapular artery and nerve. Other letters 

 in text. 



The deltoid (text-fig. 10, D.M) is very powerful, and its super- 

 ficial fibres are fused with those of the pectoralis major. It has 

 an extensive origin from the whole of the ventral surface of the 

 clavicle except the sternal end, the acromion, and outer two-thirds 

 of the spine of the scapula. And the fibres arising from the 

 acromion are tendinous. All converge to the usual deltoid 

 insertion. 



The teres major (text-fig. 11,1) has the same origin and insertion 

 as in Man, bnt it is intimately blended with the latissimus dorsi 

 and dorso-epitrochlearis. The teres mhwr has also an origin 

 similar to that in Man, but its tendon of insertion is pushed on tc 

 the humerus distal to the greater tuberosit}\ 



