Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: / / terior and posterior circumflex arteries arise at the same level as the subscapular, and they form an arterial ring round the surgical neck of the humerus. The anterior proceeds outwards under the coraco-brachialis and both heads of the biceps to anastomose under cover of the deltoid with the posterior circumflex. On the way it sends a branch up the bicipital groove into the shoulder joint. The posterior circumflex artery is larger than the anterior. It passes directly backwards through the quadrilateral space in company with the circumflex nerve. It then sweeps forwards round the surgical neck of the humerus, freely supplying the deltoid all the time. The axillary vein begins at the lower border of the teres major, or perhaps higher up, by the union of the basilic vein with the companion veins of the brachial artery. It runs upwards along the inner aspect of the artery and ends at the outer border of the first rib by changing name into subclavian. Its tributaries correspond to the branches of the artery and it receives in addition the cephalic vein. The external inte,rn,aland posterior cords of the brachial plexus lie together on the outer aspect of, the first part of the artery; they arrange themselves according to their names on the corresponding aspect of the second part; while their eight terminal branches are distributed round the third part of the artery as already noted. The external cord gives off the external anterior thoracic nerve and then divides into the musculo-cutaneous and the outer head of the median. The external anterior thoracic nerve pierces the costo-coracoid membrane and supplies the pectoralis major. The musculo-cutaneous nerve leaves the axilla by piercingthe coraco-irachialis and will be studied later. The internal cord of the plexus g...