THE SKELETON. 53 
A slight constriction between the base of the spine and 
the margin of the glenoid cavity is termed the neck. From 
“fre yp f* S54 
Me 
Fic. 30. LATERAL or Outer ASPECT OF THE SCAPULA. 
ac, Acromion process; ax, axillary border; c, coracoid process; gi, 
glenoid cavity; m, metacromion process; sc, suprascapular notch; 
Sp, spine; sup. fos, supraspinous fossa; vr, vertebral border; n, neck. 
the cranial side of the latter the coracoid process curves 
mediad. 
The clavicle is a slender 
curved bone, about one inch 
long, imbedded in the mus- 
cle between the manubrium — Fy¢, 31.—Caunar Aspect oF Lert 
and the coracoid process __ CLAVICLE. 
(Fig. 21). It does not ar- b, Medial end; a, lateral end. 
ticulate with any bone, but is held in place by the cephalo- 
humeral and cleidomastoid muscles (Fig. 48). 
The shoulder girdle varies somewhat among the Mam- 
malia. The clavicle is never fully developed in any of the 
Carnivora. Primates, Chiroptera, Edentata, and Monotre- 
mata are the only orders in which all the species possess 
clavicles. A third element of the shoulder girdle, known as 
the coracoid, is a fully developed bone only in the Monotre- 
