ANATOMY OF THE ANTHEOPOID APES. 206 



§ 4. The Muscular Anatomy of the Fore Limb. 



(1) Pectoralis mff^'or (Plate XXVIII. fig. 4, Pect.l). — This muscle is divided into two 

 distinct portions, separated by a distance of an inch and a half at their origin, but 

 gradually converging towards their common insertion. The posterior half of the 

 muscle is rather more than an inch and a half wide at its origin ; its fibres arise from 

 the sternal part of the 3rd, 4th, and 5th ribs and from the edge of the sternum 

 adjacent ; at its origin the muscle is flat and thin, but gradually gets thicker as well 

 as narrower ; at about an inch before its insertion it again widens out, and is formed ot 

 a wide flat tendon and a narrow muscular strip. The anterior half of the muscle is 

 thick and narrow, being approximately of the same diameter throughout, except at the 

 insertion, where it becomes wider and thinner; it arises by a head, measuring rather 

 less than one-third of an inch in diameter, just below the omohyoid of its side from the 

 sternum ; it has no connection whatever with the clavicle. It becomes fused with the 

 second part of the pectoral just before their common insertion and lies above it; the 

 line of insertion of the pectoral upon the forearm measures two inches and a half, 

 and commences from the head of the humerus just above the biceps ; it is tendinous 

 on the lower surface but muscular above. 



(2) Pectoralis minor (Plate XXVIII. fig. 4, Pect.2). — This muscle is composed of 

 two perfectly distinct parts : the first arises from the third and fourth ribs at the 

 junction of the bony ribs with their cartilaginous portions ; it is partly overlapped at 

 its origin by the second part of the muscle. It measures one inch and a quarter in 

 greatest breadth, and rapidly narrows to the tendon of insertion, which commences (on 

 the inferior surface of the muscle) an inch and a half from the actual insertion. 



(3) The second half of the Pectoralis minor has a broad thin origin from ribs four, 

 five, and six ; but the muscle is already very narrow before it becomes free from the 

 attachment at its origin. It is inserted by a long and narrow tendon just above and in 

 common with the anterior extremity of the tendinous insertion of the jjectoralis major 

 on to the head of the humerus. 



The sterno-clavicular ligament is attached to the coracoid process in common with 

 the tendon of the anterior part of the pectoralis minor; its entire length is two 

 inches and three-fifths ; it arises by a few fibres from the anterior end of the sternum 

 in front and to the outside of the origin of the pectoralis major. It is figured by 

 Miss Westling. 



(4) Coraco-brachialis arises in common with the biceps from the coracoid process; 

 the apparent attachment of the muscle is along a line two inches and three-fifths in 

 length; it is, however, really fixed to the humerus by two separate attachments, 

 between which intervenes a thick tendinous ridge attached at both its ends to the 

 humerus, but free m the middle ; upon these are inserted some of the fibres of the 

 coraco-brachialis ; the anterior end of the tendon is attached to the flat broad tendon 



