178 The Development of the Arm in Man 



considerable interval of fascia connecting them to the neural processes 

 of the lower cervical and the thoracic vertebrae. There is a tendonous 

 attachment to the clavicle and acromion and into fascia or condensed 

 tissne on the surface of the infraspinatus between the trapezius and the 

 deltoid. 



The rliomhoid muscle lies in the region of the seventh cervical to the 

 fourth thoracic vertebrae. It is inserted into the condensed tissue along 

 the dorsal border of the scapula. 



The latissimus dorsi muscle fibers extend from the humerus to the 

 level of the ninth rib. There is a considerable interval of fascia be- 

 tween them and the neural processes of the lower thoracic and the first 

 two or three lumbar vertebrae. This dorsal fascia is not very well 

 marked. The latissimus also has fibers attached to the condensed tissue 

 at the inferior angle of the scapula. 



The serratus anterior muscle is separate from the levator scapulae 

 except near its attachment to the scapula. It is a broad, thin sheet, 

 having digitations to the first eight ribs. 



The pedoralis major muscle is well developed. The separation be- 

 tween the clavicular and the sterno-costal portions is less marked than 

 in the preceding stage.' The muscle is attached as low as the sixth rib. 



The pedoralis minor muscle is quite distinct from the major, as a 

 considerable layer of loose mesenchymal tissue lies between them. It 

 arises from the second, third and fourth ribs and passes to the coracoid 

 process. 



The siibclavius muscle is inserted into the clavicle at an angle of 

 45°. As the scapula and clavicle sink down towards the level of the 

 first rib the angle at which this muscle is inserted into the clavicle 

 decreases. 



The teres major muscle arises from the lower angle of the scapula and 

 passes to the humerus. It is interesting to note that at this stage 

 tendon of the latissimus dorsi twists around the lower l^order of the 

 teres to be inserted with it into the humerus. 



The deltoid muscle is large and well developed. 



The suprasfinatus muscle arises from the thickened anterior border 

 of the scapula. It cannot be said to take origin more from the lateral 

 surface than from the median surface of the scapula. 



The infraspinatus muscle occupies the middle of the lateral surface 

 of the scapula and passes beneath the deltoid to the great tuberosity of 

 the humerus. 



The suhscapularis muscle arises from most of the median surface of 



