114 MUSCULAR SYSTEM. 



Relations. — Externally, with the panniculus and triceps mus- 

 cles ; internally, with the aponeurosis of the external oblique, 

 the serratus magnus, and the ribs : inferiorly, with its fellow, and 

 in part concealed by the next muscle. 



Direction. — Longitudinal : inclining upwards. 



Structure. — Fleshy: only that its anterior end is in part apo- 

 neurotic. 



Action. — To draw the head of the humerus, and along with 

 it the lower end of the scapula, backwards, throwing the latter 

 more into the upright position. 



PECTORALIS PARVUS. 



Situation. — Below the former muscle. 



Attachment. — Inwardly, to the side of the anterior half of the 

 sternum, and to the cartilages of the first four ribs : outwardly, 

 to the faschia covering the muscles in front of the scapula and 

 shoulder-joint, extending nearly as high up as the place of origin 

 of the antea-spinatus. 



Relations. — Superiorly and externally, with the preceding 

 muscle ; inferiorly, with the pectoralis transversus ; internally, 

 with the cartilages of the ribs ; anteriorly, with the levator 

 humeri. 



Structure.— Fleshy ; excepting its inferior termination, which 

 is aponeurotic. Its fleshy parts are formed into layers, one over- 

 lapping another. 



Action. — To assist the pectoralis magnus. 



3.— COSTAL REGION. 



Comprehending muscles which have, all of them, extensive 

 attachments to the ribs. 



C Costo-subscapularis. 



SERRATUS MAGNU S. < DorSO-COStalis . 



(^ Lunibo-costalis. 



Situation. — Between the shoulder and the side of the chest. 



Figure. — In outline, semicircular: fibres radiating from a centre, 

 and forming an indentated or serrated circumferent border. 



Attachment. — Anteriorly, to the bodies and transverse pro- 

 cesses of the 4th, 5th, 6th and 7th cervical vertebrae ; posteri- 

 orly, to the eight anterior ribs, as low down as their cartilages, 

 by as many fleshy digitations : outwardly, to the upper and inner 

 part of the scapula, occupying the space between the origin of 

 the subscapularis and the insertion of the rhomboidei. 



Relations. — Externally, with the scapula ; internally, with 

 the cervical portion of the longissimus dorsi, the cervical verte- 



