1 86 A MANUAL OF ANATOMY 



pierced by numerous nutrient foramina. The great tuberosity is 

 situated obliquely on the outer surface, immediately beyond the 

 anatomical neck. It presents three fiat muscular impressions — an 

 upper for the insertion of the supraspinatus, a middle for the infra- 

 spinatus, and a lower for the teres minor, which latter muscle con- 

 tinues to take insertion into a rough marking on the shaft for at 

 least i inch below the lower impression. The small tuberosity is 

 an oval prominence situated on the anterior aspect, immediately 

 beyond the anatomical neck. It gives insertion to the subscapu- 

 lari§, which continues to take insertion into the adjacent part of 

 the shaft for about \ inch. The commencement of the bicipital 

 groove, which lodges the long tendon of the biceps, lies between the 

 two tuberosities, where it is bridged over by the transverse humeral 

 ligament. It presents a large nutrient foramen close to the great 

 tuberosity for an offset of the ascending branch of the anterior 

 circumflex artery. The surgical neck is the constriction below the 

 tuberosities. 



The upper extremity of the humerus receives its principal blood- 

 supply from the anterior and posterior circumflex arteries. 



The shaft is almost cylindrical in its upper half, but it is laterally 

 expanded and triangular in its lower half. The anterior aspect 

 presents superiorly the bicipital groove, which commences between 

 the tuberosities, where it is deep, and passes downwards and slightly 

 inwards, terminating about the junction of the upper and middle 

 thirds. It is bounded by two rough ridges, outer and inner. The 

 outer bicipital ridge^ which is the more prominent, gives insertion 

 over about its lower three-fourths to the pectoralis major, this portion 

 being called the pectoral ridge. It is in line with the anterior border 

 of the lower half of the shaft. The inner bicipital ridge gives inser- 

 tion over about its lower two-thirds to the teres major, this portion 

 being known as the teres ridge. It is in line with the internal border 

 of the lower half of the shaft. The floor of the groove over about 

 its middle third gives insertion to the latissimus dorsi. The groove 

 is occupied by the long tendon of the biceps, invested by a 

 tubular prolongation of the synovial membrane of the shoulder- joint ; 

 and the ascending branch of the anterior circumflex artery. The 

 outer aspect of the shaft presents a rough V-shaped mark, called the 

 deltoid impression, for the insertion of the deltoid. The point of 

 the V, which is embraced by two slips of the brachialis anticus, is 

 at the centre of the shaft, whence it extends upwards for about 

 2 inches. Its anterior margin is in line with the pectoral ridge, and 

 its posterior margin bounds superiorly the lower part of the spiral 

 groove. On the inner aspect of the shaft, about the centre, there is a 

 rough line about lA inches long, placed in the course of the internal 

 border, for the insertion of the coraco-brachialis. Immediately 

 below this line is the principal medullary foramen for the nutrient 

 or medullary branch of the brachial artery, the canal to which it 

 leads being directed downwards. The posterior and external aspects 

 of the upper part of the shaft present a winding groove, called the 



