450 DR. R. BROOM ON THE EARLY CONDITION OF THE 
The plane of the girdle lies as near as may be at right angles to 
the axis of the cervical vertebre. The scapula (PI. 41. fig. 1, sc.) 
in its lower two-thirds is a narrow, somewhat flattened rod, while 
above it expands into a relatively rather large antero-posteriorly 
directed plate. From the anterior border of the scapula, at a point 
near the union of the lower and the middle third, a well-developed 
acromion process (ac.) arises, and passes first forwards and 
slightly outwards and upwards, and then downwards and inwards 
to meet the clavicle (c/.). The lower end of the scapula forms 
with the coracoid (co.) the glenoid cavity. From along the 
upper border of the upper part of the acromion to the anterior 
border of the middle third of the scapula there stretches a thin 
bony plate, forming the scapular spine (sp.). 
The coracoid (co.), which is about half the length of the 
scapula, and about as wide as the scapula is in its middle region, 
passes inwards, a little downwards, and very slightly forwards 
from its point of union with the lower end of the scapula, and 
forms an articulation with the side of the broad presternum 
(fig. 2, p.st.), just in front of the first rib. The inner end of the 
coracoid is slightly dilated, and while its posterior half forms the 
joint with the sternum, the anterior portion passes forwards 
towards the clavicle, and is continued into the undifferentiated 
tissue which surrounds that. bone. 
The clavicle (c.) is a well-developed little osseous bar which 
passes directly outwards from near the anterior end of the 
sternum for some distance, and then turns abruptly upwards to 
meet the end of the acromion. The bone is surrounded by a 
thick layer of undifferentiated tissue, but no cartilage can be 
detected in connection with it. 
The sternum (s¢.) is chiefly characterized by the great breadth 
of its anterior part—the presternum being about three times as 
wide as the posterior portion. From its widest point it 
eradually narrows to the point of union with the fourth rib; 
while in the posterior half the width is moderately uniform. 
There is a distinct xiphisternum (#.st.). The sternum gives 
attachment to eight pairs of ribs. Anteriorly the presternum 
ends rather abruptly, in marked contrast to the pointed condition 
of the anterior end in later stages. 
The omosternum is not yet formed, and is represented by a 
mass of undifferentiated tissue between the inner end of the 
clavicle and the sternum. 
