3i8 



A MANUAL OF ANATOMY 



the lower border of the subscapularis muscle, in contact with the 

 subscapular artery. Their afferent vessels are derived from (i) the 

 superficial lymphatics of the lower and back part of the neck, 

 (2) the superficial lymphatics of the posterior part of the trunk, 

 and (3) some of the superficial lymphatics of the supra-umbilical 

 portion of the lateral wall of the abdomen. Their efferent lym- 

 phatics pass to (i) the external axillary glands, (2) the central 

 axillary glands, and (3) the infra-clavicular glands. 



The central glands are about five in number, and are situated at the 

 base of the axilla. They lie upon the axillary fascia, and between 

 the external, pectoral, and subscapular groups. They receive as 

 afferent vessels some of the efferent vessels of the external, pectoral, 



and subscapular glands. 

 Their efferent vessels pass to 

 the infra-clavicular glands. 

 Serratus Magnus — Origin. — 

 The outer surfaces of the first 

 eight or nine ribs about midway 

 between the angles 

 Subscapularis ^nd costal Cartilages, 

 by means of fleshy serrations 

 which are curved with their 

 convexities forwards. Each ser- 

 ration arises from one rib, ex- 

 cept the first, which arises from 

 the first and second ribs and a 

 fibrous arch between them. 



Insertion. — ^The anterior 

 Obhquu. surface of the base of the 



Externus i r ,, 



,. , . scapula from the superior 



Abdominis i i^, • r • , ^ 



to the mferior angle. 

 Nerve - supply. — The posterior 

 thoracic nerve, which arises by 

 three roots from the fifth, sixth, 

 and seventh cervical. The nerve 

 descends on the axillary surface 

 of the muscle. 



The muscle is arranged in three parts. The upper part is formed 

 by the first serration, which is of large size, and it is inserted 

 into the triangular area on the front of the superior angle of the 

 scapula. The middle part forms a thin, expanded sheet, which is 

 formed by the broad second and the third serrations, and it is inserted 

 into the long, linear impression on the front of the base, reaching 

 to near the superior angle and extending down to near the inferior 

 angle. The lower part, which is formed by the lower five or six 

 serrations, is fan-shaped, and towards the scapula is thick and 

 stout, its insertion being into the expanded area in front of the 

 inferior angle. The lower four or five serrations interdigitate with 

 the obliquus externus abdominis. 

 Action. — ^The muscle draws the base of the scapula forwards, as 



Fig. 179.- 



-The Serratus Magnus 

 Muscle. 



