THE SCAPULA. 183 
means of the coraco-acromial ligament. Its under surface is smooth and overhangs 
the shoulder joint. 
The supraspinous fossa, of much less extent than the infraspinous, 1s placed 
above the spine, the upper surface of which assists in forming its curved floor; in 
it 1s lodged the supraspinatnus muscle. The suprascapular notch opens into it above, 
whilst below and exter nally it communicates with the infraspinous fossa by the 
great scapular notch, through which the suprascapular artery and nerve pass to 
reach the infraspinous fossa. 
The infraspinous fossa, overhung by the spine above, is of triangular form. The 
axillary border of the bone limits it in front, whilst the vertebral margin bounds it 
behind; the greater part of this surface affords origin to the infraspinatus muscle, 
excepting a well-defined area which skirts the axillary border and inferior angle of 
the bone, and which affords an attachment to the fibres of origin of the teres minor. 
This muscle extends along the posterior surface of the axillary border in its upper 
two-thirds, reaching nearly as high as the glenoid edge; whilst a crescentic surface, 
which occupies the lower third of the axillary border and curves backward round 
the posterior aspect of the inferior angle, furnishes an origin for the teres major 
muscle. Here also, near the inferior angle, are occasionally attached some of the 
fibres of the latissimus dorsi muscle. 
The ventral aspect (facies costalis) of the body is hollow from above downwards and 
from side to side, the greatest depth being in correspondence with the spring of the 
spine trom the dorsal surface. Its inner boundary, which is formed by the anterior 
lipped edge of the vertebral border, affords attachment to the fibres of insertion of 
the serratus magnus along the greater part of its extent. The area of insertion of 
this muscle is, however, considerably increased over the anterior aspects of the 
superior and inferior angles respectively. Running down from the head and neck 
above to the inferior angle below, there is a stout rounded ridge of bone, which 
imparts a fulness to the anterior aspect of the axillary border "and increases the 
depth of the ventral hollow ; to this, as well as to the floor of the fossa, the sub- 
scapularis muscle is attached. The tendinous intersections of this muscle leave 
their imprint on this surface of the bone in a series of three or four rough lines 
which converge towards the neck. 
Nutrient Foramina.—Foramina for the passage of nutrient vessels are seen in different parts 
of the bone; the most constant in position is one which opens into the infraspimous fossa, about an 
inch or so from the scapular notch. Others are met with on the upper and under surfaces of the 
spine, on the ventral aspect near its deepest part, and also around the glenoid margin. 
‘Connexions.—The scapula is not directly connected with the trunk, but articulates with the 
outer end of the clavicle, in union with which it forms the shoulder girdle supporting the 
humerus on its glenoid surface. Placed on the upper and back part of the thorax, it covers the 
ribs from the second to the seventh inclusive. Possessed of a wide range of movement, it alters 
its position according to the attitude of the limb, rising or falling, being drawn inwards or 
outwards, or being rotated upon itself according as the arm is moved in various directions. These 
changes in position can easily be determined by recognising the altered relations of the subcutaneous 
and bony prominences, more especially the former, “which include the spine, the acromion process, 
and the lower half of the vertebral border. 
Architecture.—For so light and thin a bone, the scapula possesses a remarkable 1 rigidity. This 
is owing to the arrangement ‘of its parts. Stout and thick where it supports the elenoid surface 
and coracoid process, the rest of the bone is thin, except along the axillary border Dut strength is 
imparted to the body by the manner in which the spine is fused at right angles to its p sterior surface. 
Variations.—The most common variation met with is a separated acromion process., In 
- these eases there has been failure in the ossific union between the spine and acromion, the 
junction between the two being effected by a layer of cartilage cr an articulation possessing a 
joint cavity. The condition is usually symmetrical on both sides, though instances are recorded 
where this arrangement is unilateral. Very much rarer is the condition in which the coracoid 
process is separable from the rest of the bone. The size and form of the suprascapular notch 
differs. In certain cases the superior border of the bone describes a uniform curve reaching the 
hase of the coracoid without any indication of a notch. In some scapulie, more particul: uly in 
those of very old people, the floor of the subse apular fossa is deficient owing to the aqsorption of 
the thin bone, the periosteal layers alone filling up the gap. 
At birth the vertical length of the bone is Tess in proportion to its width than in the adult. 
Ossification.— Ossification begins in the body of the cartilaginous se apula about the 
end of the second month of feetal life. At birth the head, neck, body, spine, and base of 
the coracoid process are well defined ; the vertebral Border , Inferior ‘angle, elenoid fossa, 
acromion and coracoid processes, are still cartilaginous. The centre for the upper and 
