208 THE MUSCLES AND FASCI.E OF THE UPPER LIMB. 



the neck. It lies over the splenius colli. cervicalis ascendens, posterior scapular artery, and 

 first two ribs. 



Varieties. The number of vertebral attachments of the levator anguli scapulae is subject 

 to frequent variations. A slip has been observed to extend to it from the occipital or from 

 the mastoid process of the temporal bone. It often appears as a divided muscle, the parts 

 connected with the several vertebras remaining- separate, even to the place of insertion. It is 

 occasionally connected by slips with the trapezius, scalene, or serrated muscles, or sends a 

 fasciculus to the first or second rib. In quadrupeds it is united with the serratus mag-nus, so 

 as to form a single muscle. Appearing- as a detached bundle of the levator anguli scapulae, 

 there is sometimes a muscular slip passing 1 from the transverse processes of one or two upper 

 cervical vertebrae to the outer end of the clavicle, and representing 1 the Jcrntor clamcul<r 

 muscle of the lower animals. 



Nerves of the preceding: muscles. The trapezius muscle receives its nerves from the 

 spinal accessory and from the third and fourth cervical nerves. The latissimus dor si is 

 supplied by the long- subscapular nerve of the brachial plexus (7, 8 c). 1 The nerve of the 

 rhomboid muscles proceeds from the fifth cervical, and the levator scapulas is supplied from 

 the third, fourth, and fifth cervical nerves. 



BETWEEN THE TRUNK AND THE UPPER LIMB ANTERIORLY. 



The superficial fascia of the pectoral region encloses the mam- 

 mary gland, covering ifc both in front and behind, and sending strong septa in 

 between its lobes. Processes likewise extend forwards from the fascia! investment 

 of the gland, between the masses of fat, to the skin and nipple, thus affording sup- 

 port to the gland. 



The deep fascia of the pectoral region is for the most part thin and unim- 

 portant. Covering the pectoralis major, it is attached above to the clavicle and 

 internally to the front of the sternum, while externally and below it becomes con- 

 tinuous with the fascia of the shoulder, of the axilla, and of the side of the chest. 

 As a development of the deep fascia there may be specially noticed the costo-coracoid 

 membrane, which is a strong fibrous structure, placed behind the pectoralis major, 

 and attached superiorly to the clavicle in two layers which ensheath the subclavius 

 muscle, and the posterior of which is blended with the front of the sheath of the 

 axillary vessels, derived from the deep fascia of the neck. The strong lower margin 

 of the membrane, distinguished sometimes as the costo-coracoid ligament, extends 

 from the coracoid process to the first rib at the origin of the subclavius muscle. 

 From this membrane a thin lamina is prolonged downwards to the pectoralis minor, 

 which it invests ; and being continued beyond that muscle, it stretches across as a 

 firm membrane between the pectoralis minor and the short head of the biceps, 

 and ends below by joining the axillary fascia near the lower border of the pectoralis 

 major. 



The axillary fascia is a strong membrane stretched across the axilla, and so 

 disposed as to maintain the skin in position over that hollow. Beginning at the 

 lower border of the pectoralis major, where it is continuous with the fascia covering 

 that muscle, it is joined by the layer descending from the pectoralis minor, and is 

 by this means drawn upwards into the intermuscular space ; thus strengthened it 

 slopes outwards and backwards to the posterior fold of the axilla, where it is con- 

 tinued into the sheaths of the latissimus dorsi and teres major muscles. In the 

 deepest part of the axilla the fascia is perforated by numerous lymphatic vessels. At 

 the outer side, occupied by the large vessels and nerves of the limb, it is continuous 

 with the sheath of the vessels and with the aponeurosis of the arm. The density of 

 this fascia offers a considerable obstacle to the progress of axillary abscesses to the 

 surface. 



MUSCLES. The pectoralis major muscle consists of two portions, clavicular and 



1 The numerals and initial letter indicate the nerves by which the motor fibres leave the spinal 

 cord. 



