CHAP, v.] THE CAT'S MUSCLES. 147 



humerus, and extends down (between the biceps and brachialis 

 anticus to the summit of the lowest third of the humerus. It 

 is imperfectly divisible into two layers. The more superficial of 

 these Qj 2 A) arises from the more anterior part of the sternum, 

 and goes to the lower part of the insertion, while the other part 

 (p B) both arises and is inserted for the whole length of the 

 origin and insertion of the second part. 



(3.) The third part (p*) arises from the sternum between the 

 second and sixth costal cartilages. It is inserted into the head 

 of the humerus between the tuberosities by strong fascia closely 

 connected with that of the supra-spinatus muscle. It is also 

 inserted by muscular fibres for a short distance into the front 

 of the humerus just below the great tuberosity. 

 (4.) The fourth part is the most posterior in origin. It is long 

 and narrow, and its fibres run more antero-posteriorly than do 

 the others. It arises from the sternum between the fifth costal 

 cartilage and the root of the xiphoid. Towards its insertion it 

 blends with the ventral part of the latissimus dorsi, and some 

 of its fibres are inserted into the fascia in the neighbourhood 

 of the axilla. Its main insertion is (by strong fascia) into the 

 inner side of the deltoid ridge of the humerus below, and on 

 the inner side of the insertion of the third part. 

 (5.) The fifth, and much the smallest part, is the most an- 

 terior (p 5 ). It arises from the side of the manubrium, covered 

 by, and more or less blended with, the second part of the 

 pectoralis. It passes outwards, becoming slightly connected 

 with the clavicle, and is inserted into the humerus just above 

 the insertion of the second part. It may be called the sub- 

 clavicualr part of the pectoralis. 



This muscle adducts the humerus, and enables the cat to give a 

 powerful blow with the paw inwards. If the arm be fixed, it then 

 tends to draw the body forwards or, in climbing, upwards. 



The cephalo'humcml is a large muscle which arises conterminously, 

 and more or less blended with the anterior part of the trapezius. 

 Its main part takes origin from the back of the skull and the lamb- 

 doidal ridge, and from fascia in the middle of the neck (Fig. 77, Ch). 

 It passes down outside the clavicle (with which it contracts a 

 slight adhesion) and outside the biceps covering the front of the 

 upper arm. Near the elbow-joint it fuses with the brachialis 

 anticus (passing to the outer side and front of the biceps), and is 

 inserted into the coronoid process of the ulna, having first received 

 an addition from the first part of the pectoralis. 



The third part of the deltoid fuses anteriorly with the cephalo- 

 humeral. 



The deltoid consists of three portions : (Fig. 80, D 2 \ a part which 

 arises from the scapula between, and from, the acromion and met- 

 acromion processes ; and (D 1 ) a part which arises from the hinder side 

 of the scapular spine, conterminous with the insertion of the anterior 



part of the trapezius. 



r L 2 



