64 ANTHROPOLOGY. 
Of these, one is connected to the clavicle (subclavius), two to the humerus 
(pectoralis major and latissimus dorst), and eight to the scapula, viz. trape- 
ztus, levator angulc scapule, omo-hyoid, rhomboides major and minor, 
serratus magnus, pectoralis minor, and latissimus dorsi. The muscles of the 
upper extremity are classed into those of the shoulder and arm, forearm, 
and hand. 
1. MUSCLES OF THE SHOULDER AND ARM. These muscles are hidden 
from view by the supra-spinous, infra-spinous, and subscapular fascise, and 
the brachial aponeurosis, which have already been briefly described. The 
proper muscles are six in number: the deltoid, supra and infra spinatus, 
teres minor and major, and the subscapularis. Those of the arm are four: 
the biceps, coraco-brachialis, brachialis anticus, and triceps. 
The deltoides is a very thick, strong, and triangular muscle, bent so as to 
embrace the shoulder-joint in front, externally and behind. It arises from 
the lower edge of the spine of the scapula and from the anterior edge of 
the acromion process, and from the external third of the clavicle; its in- 
sertion is into a rough surface about two inches in extent situated on the 
outer side of the humerus, and commencing just above its centre. It 
abducts and raises the arm, draws it forwards or backwards, and rotates it 
inwards or outwards. * 
Supra-spinatus fills the fossa of the same name, and arises from all that 
portion of the scapula above its spine, as also from a strong fascia which 
covers the muscle; it is inserted into the upper and fore part of the great 
tuberosity of the humerus, into the most anterior and superior of the three 
depressions which are marked on that surface. It assists the deltoid in 
raising and abducting the arm, strengthens the capsular ligament, and acts 
as antagonist to the pectoral, deltoid, and other muscles in proves a 
tendency to dislocation. 
Infra-spinatus is inferior to the last, flat, and triangular. It arises from 
the inferior surface of the spine of the scapula and from the dorsum of this 
bone as far down as the posterior ridge on the inferior costa; it 1s inserted 
into the middle of the external or greater tuberosity of the humerus below 
the infra-spinatus. Its use is to assist the superior part of the deltoid in 
raising the arm, drawing it backwards, and rotating it outwards; it also 
_ serves to strengthen the articulation. 
Teres minor is a small muscle inseparably attached along the lower edge 
of the last muscle. It arises from a depression between the two ridges on 
the inferior costa of the scapula, and is inserted below the infra-spinatus 
mto the inferior depression on the great tuberosity of the humerus, and into 
the bone a little lower down. It co-operates with the last muscle. 
Sub-scapularis is a broad, triangular muscle, situated on the inner side of 
the scapula opposite to the three last mentioned muscles. It arises from 
all the surface and circumference of the subscapular fossa, and is inserted 
~ into the interval or small tubercle of the humerus. As the strongest of the 
capsular muscles, it strengthens the inner side of the articulation and 
guards against dislocation. | 
_ Teres major, a long and flat muscle, arises from a rough flat surface on 
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