THE SKELETON OF THE DOG. PECTORAL GIRDLE. 405 



being directed downwards and forwards, and being expanded 

 to form the shallow glenoid cavity with which the head of 

 the humerus articulates. The inner surface of the scapula is 

 nearly flat, while the outer is drawn out into a very prominent 

 ridge, the spine, which, arising gradually near the dorsal end, 

 runs downwards, dividing the surface into two nearly equal 

 parts, the prescapular and postscapular fossae, and ends 

 in a short blunt process, the acromion. The anterior border 

 of the scapula is somewhat curved, and is called the coracoid 

 border ; it is terminated ventrally by a slight blunt swelling, 

 the coracoid process, which ossifies from a different centre 

 from the rest of the scapula, and is probably the sole repre- 

 sentative of the coracoid. The dorsal or suprascapular 

 border of the scapula is rounded, while the posterior or 

 glenoid border is nearly straight. The clavicle 1 or collar 

 bone, which in a large proportion of mammals is well seen, in 

 the dog is very imperfectly developed ; it is short and broad, 

 and is suspended in the muscles, not reaching either the 

 scapula or sternum. 



THE ANTERIOR LIMB. 



The anterior limb of the dog is divisible into the usual 

 three portions, the brachium or upper arm, the anti- 

 brachium or fore-arm, and the manus or wrist and hand. 



The brachium or upper arm includes only a single bone, 

 the humerus. 



The humerus is a stout elongated bone, articulating by 

 its large proximal head (fig. 77, 1) with the glenoid cavity of 

 the scapula, and at its distal end by the trochlea with the 

 bones of the fore- arm. The head passes on its inner side into 

 an area roughened for the attachment of, muscles and called 

 the lesser tuberosity (fig. 77, 2) ; while in front it is divided 

 by the shallow bicipital groove from a large roughened area, 

 the greater tuberosity (fig. 77, 3), which is continued as a 



1 See note to p. 25. 



