180 SPECIAL ANATOMY OF THE SKELETON 



obtuse angle with the shaft. It is more distinctly marked in the lower half of 

 its circumference than in the upper half, where it presents a narrow groove, 

 separating the head from the tuberosities. Its circumference affords attachment 

 to the capsular ligament and is perforated by numerous vascular foramina. 



The Greater Tuberosity (tuberculum majus). The greater tuberosity is situated 

 on the outer side of the head and lesser tuberosity. Its upper surface is rounded 

 and marked by three flat facets, separated by two slight ridges; the highest facet 

 gives attachment to the tendon of the Supraspinatus; the middle one, to the Infra- 

 spinatus; the inferior facet and the shaft of the bone below it, to the Teres minor. 

 The outer surface of the great tuberosity is convex, rough, and continuous with 

 the outer side of the shaft. 



The Lesser Tuberosity (tuberculum minus). The lesser tuberosity is more 

 prominent, although smaller than the greater; it is situated in front of the head, 

 and is directed inward and forward. Its summit presents a prominent facet 

 for the insertion of the tendon of the Subscapularis muscle. The tuberosities 

 are separated from each other by a deep groove, the bicipital groove (sulcus inter- 

 tubercular is). This groove lodges the long tendon of the Biceps muscle, accom- 

 panied by a branch of the anterior circumflex artery. It commences above be- 

 tween the two tuberosities, passes obliquely downward and a little inward, and 

 terminates at the junction of the upper with the middle third of the bone. It is 

 deep and narrow at the commencement, and becomes shallow and a little broader 

 as it descends. In the recent state it is covered with a thin layer of cartilage, 

 lined by a prolongation of the synovial membrane of the shoulder-joint, and 

 receives the tendon of insertion of the Latissimus dorsi muscle. 



The Shaft (corpus humeri). The shaft* of the humerus is almost cylindrical 

 in the upper half of its extent, prismatic and flattened below, and presents three 

 borders and three surfaces for examination. 



The anterior border runs from the front of the greater tuberosity above to the 

 coronoid depression below, separating the internal from the external surface. 

 Its upper part is very prominent and rough, forms the outer lip of the bicipital 

 groove, and serves for the attachment of the tendon of the Pectoralis major. 

 About its centre it forms the anterior boundary of the rough deltoid impression 

 (tuberositas deltoidea); below, it is smooth and rounded, affording attachment 

 to the Brachialis anticus muscle. 



The external border (margo lateralis) runs from the back part of the greater 

 tuberosity to the external condyle, and separates the external from the posterior 

 surface. It is rounded and indistinctly marked in its upper half, serving for the 

 attachment of the lower part of the insertion of the Teres minor muscle, and below 

 this of the external head of the Triceps muscle; its centre is traversed by a broad, 

 but shallow, oblique depression, the musculospiral groove (sulcus nervi radialis); 

 its lower part is marked by a prominent, rough margin, a little curved from 

 behind forward, the external supracondylar ridge, which presents an anterior lip 

 for the attachment of the Brachioradialis above and Extensor carpi radialis 

 longior below, a posterior lip for the Triceps, and an intermediate space for the 

 attachment of the external intermuscular septum. 



The internal border (margo medialis) extends from the lesser tuberosity to the 

 internal condyle. Its upper third is marked by a prominent ridge, forming 

 the internal lip of the bicipital groove, and gives attachment to the tendon of the 

 Teres major. About its centre is an impression for the attachment of the Coraco- 

 brachialis, and just below this is seen the entrance of the nutrient canal, directed 

 downward. Sometimes there is a second canal situated at the commencement 

 of the musculospiral groove, for a nutrient artery derived from the superior pro- 

 funda branch of the brachial artery. The inferior third of this border is raised 

 into a slight ridge, the internal supracondylar ridge, which becomes very prominent 



