72 Anatomy of Skeleton 



ridge carried out on its outer aspect. The covering of Subscapularis is really respon- 

 sible for the axillary border as a ridge, and so we find that the origin of this muscle 

 extends out to the axillary border, and follows this even when, as frequently occurs, 

 it turns on to the dorsal surface for a little distance between the Teres major and minor 

 (Fig. 57). The line of origin of Subscapularis extends along the border as far up as 

 the origin of the Triceps. Its inner limit is made by the area for Serratus magnus, 

 as already mentioned, and its margin reaches the top border of the bone in front of 

 the upper and inner angle, and runs along this border as far as the suprascapular notch. 

 The outer limit of its origin between this point and the axillary border is somewhat 

 variable : the muscle marking given in the figure may be taken as an average type, 

 and the concave irregular line passes inside the foramina found in the ventral fossa, 

 which are for small vessels belonging to the suprascapular system. Observe now that 

 the area of origin is marked by a variable number of secondary ridges, all converging 

 in the direction of the fibres of the muscle : these are evidently for intramuscular 

 tendinous slips, which increase the area of origin of the muscle so that it forms an 

 exceedingly thick mass. If the bones are articulated and a line drawn to represent 

 the lower border of the muscle, from the lowest point of its origin to the lowest point of 

 insertion, it is evident that its inferior border comes down a Considerable distance 

 below the axillary margin of the scapula, as shown in the figures. 



The outer third of the ventral surface is covered by the Subscapularis, which plays 

 over it without arising from it. As it gets near the neck the subscapular bursa separates 

 it from the bone, and the coracoid process arches forward over the top of its tendon : 

 the subscapular bursa is frequently prolonged upwards over the tendon as a " sub- 

 coracoid bursa " between it and the concave lower aspect of the coracoid process 

 under which it plays. The subscapular bursa is also between the tendon and the inner 

 part of the capsule, and opens into the joint between the upper and middle gleno- 

 humeral ligaments, by a large aperture on and in which the upper part of the tendon lies 

 as it passes out towards the humerus. 



Dorsal Surface (see Fig. 57). 



Notice that the floors of the supra- and infra- spinous fossae are in different planes, 

 depending on the relations of their contained muscles to the rounded end of the 

 humerus. It is this difference in planes that really makes the subscapular hollow on 

 the bone, for this hollow corresponds with the base of the spine, where the two planes 

 meet at an angle (130 degrees) with each other as well as with the spine. It can be seen 

 that the bone below the level of the spine is slightly concave, that is, it is slightly con- 

 vex on the ventral side, and in the early embryonic condition the scapula is decidedly 

 convex on its ventral aspect, and does not possess a supraspinous fossa : the Supra- 

 spinatus is at first a very small rudiment attached only to the upper and outer border 

 of the bone, and as it extends it forms a fossa, and this in its turn makes an angle with 

 the lower plate which is the subscapular hollow (see Fig. 58). 



The two muscles that occupy the fossae extend their origin to the vertebral border : 

 here there is a definite rim which marks the attachment of their covering aponeuroses. 

 Supraspinatus arises along the upper margin and in the fossa as far as the level of the 

 notch, where the suprascapular vessels and nerve pass between it and the bone, turning 

 slightly forward to reach the great scapular notch. Both muscles get an origin from 

 the spine of variable length, but usually extending outwards as a narrow area consider- 

 ably further than their origins from the floors of the fossae. The presence of intramuscu- 

 lar tendons in the Infraspinatus is shown by the ridges on the bony surface. The 

 aponeurosis covering Infraspinatus is strong, giving origin to muscular fibres and making 



