360 



AXILLA. 



surface, longer on the anterior, and longer still 

 at the lower edge. The surface now exposed 

 was covered by cellular tissue, and concealed 

 by the pecloralis major every where except a 

 small part of its lowest digitation, which is 

 generally to be seen below it, in contact with 

 the integuments. 



The upper edge of this muscle is nearly hori- 

 zontal, and placed about an inch below the 

 clavicle. In the space between, when some 

 fat is carefully removed, and some absorbent 

 glands, we see the axillary artery running down- 

 wards and outwards, internal and anterior to 

 which is the axillary vein, and behind it the 

 nerves. The cephalic vein is observed passing 

 upwards and inwards from the edge of the del- 

 toid muscle to the axillary vein, and the tho- 

 racica suprema artery standing forwards from 

 the axillary artery and resting on this edge of 

 the pectoral. The thoracica acromialis artery 

 runs in this space out towards the acromion 

 process, and is often a branch of the suprema. 

 Here, too, we see the lower surface of the sub- 

 clavius muscle, turned forwards, and covered 

 by a pretty strong fascia which terminates in 

 the costo-coracoid ligament. 



The costo-coracoid ligament is very thin, but 

 strong. It extends from the cartilage of the 

 first rib, just below the origin of the subclavius 

 muscle, to the coracoid process of the scapula, 

 in an arch across the vessels and nerves. It is 

 concave inferiorly, and appears to be only the 

 thickened edge of the fascia which covers the 

 subclavius and descends a little below that 

 muscle. This view of its true mode of forma- 

 tion is favoured by the fact that it has an at- 

 tachment also to the clavicle, and consequently 

 may be called costo-clcido-coracoid. The name 

 ligamentum Income is sometimes applied to in- 

 dicate its horn-shaped extremities ; Blandin 

 denominates it fascia claviculuris, and Gerdy, 

 ligament suspenscur de Vaisselle. As a ligament 

 it has little power, but as an aponeurosis it pro- 

 tects the vessels, and sends down a thin process 

 upon them. 



Below the lesser pectoral the vessels and 

 nerves again come into view, and the thoracica 

 longior or external mammary artery is seen 

 passing downwards and forwards along its 

 lower edge. For a fuller description of the pre- 

 ceding muscles, see THORAX, MUSCLES OF THE. 



The inner wall of the axilla exhibits the ribs, 

 intercostal muscles, and serratus magnus, with 

 some vessels and nerves. One of these last is 

 remarkable for its length and vertical direction; 

 it lies on the serratus magnus, and appears as 

 if flattened against the side of the thorax. It 

 arises generally by two branches from the back 

 of the anterior division of the fifth and sixth 

 cervical nerves (counting eight in the neck). It 

 communicates with the phrenic, descends be- 

 hind the brachial plexus, under the clavicle and 

 trapezius, appears upon the serratus magnus, 

 on which it runs a great distance and enters its 

 lowest division by many filaments. It is classed 

 among the respiratory nerves by Sir Charles Bell, 

 by whom it has been named the inferior ex- 

 ternal respiratory nerve of the trunk, its function 



being, according to his views, to associate the 

 muscle to which it is distributed with the ge- 

 neral respiratory movements. It was known to 

 antecedent anatomists as the posterior thoracic 

 branch of the brachial plexus.* 



Crossing the axilla from the thorax to the 

 arm, we see two nerves, frequently called nerves 

 of Wrisberg. They are the external branches, 

 or costo-humeral, of the second and third inter- 

 costal nerves. They pierce the external layer 

 of intercostal muscles opposite the origin of the 

 serratus magnus, between the second and third 

 and the third and fourth ribs, and pass out ob- 

 liquely to the arm, where they are lost in the in- 

 teguments on the inner and back part of the arm 

 and elbow. The superior of them is the larger. 



The great vessels and nerves are seen pass- 

 ing from the first rib to the lower border of the 

 teres major muscle, forming an arch whose con- 

 cavity is downwards. By raising the arm to 

 the horizontal position we obliterate the arch, 

 and by supinating the hand strongly we bring 

 them more into view. In the upper third of 

 this curve the order of the parts, proceeding 

 outwards, is, the axillary vein, axillary artery, 

 and plexus of nerves. In the middle the vein 

 is situated as before, and then the nerves sur- 

 rounding and hiding the artery ; and in the 

 inferior third we first meet the vein, then the 

 nerves, and lastly the artery. 



The axillary vein is about three inches in 

 length, commencing a little above the edge of 

 the teres major; thence it runs upwards, in- 

 wards, and forwards to the second rib, which 

 it touches, as also some fibres of the serratus 

 magnus there arising ; next it gets on the first 

 intercostal muscles, after which it becomes the 

 subclavian vein, crosses over the first rib, under 

 the clavicle, before the scalenus anticus muscle, 

 and then enters the thorax. It is formed by 

 the confluence of three veins, viz. the basilic 

 and the two vena comites which convey their 

 fluid from the fore-arm, and it is afterwards en- 

 larged by the accession of those veins which 

 accompany, usually in pairs, the subscapular, 

 the thoracic, and the circumflex arteries. It 

 also receives the cephalic a little higher up, as 

 before described. 



The axillary artery traverses this region 

 from above downwards in a course doubly ob- 

 lique, from within outwards, and from before 

 backwards; at its upper part it rests on the 

 chest separated by the serratus magnus muscle, 

 and lies close under the anterior wall of the 

 axilla, whilst below it rests on the subscapularis 

 muscle (posterior wall), and is very near the 

 arm. Its complicated relations with the nerves, 

 veins, glands, &c. come more properly under 

 consideration in the next article (AXILLARY 

 ARTERY), to which we refer. 



* One or two cases of paralysis of the serratus 

 magnus muscle from injury to this nerve have been 

 recorded. Velpeau mentions one, which resulted 

 from a blow inflicted on the inner wall of the axilla : 

 a permanent projection of the posterior edge of 

 the scapula backwards, and inability to bring that 

 bone into close apposition with the thorax, were the 

 signs on which he founded his diagnosis. (See Cy- 

 clop, of Pract. Med. art. PARALYLSIS.) ED. 



