THE SKELETON OF THE DOG. PELVIC GIRDLE. 409 



The hand has five digits, each consisting of an elongated 

 metacarpal, followed by phalanges, the last of which, the 

 ungual phalanx, is pointed and curved, and bears the claw. 

 Each of the metacarpals is seen in the young animal to have 

 its distal end formed by a prominent epiphysis, and each of 

 the phalanges, except those bearing the claws, has a similar 

 epiphysis at its proximal end. 



The pollex (fig. 80, A, I) is far shorter than the other digits, 

 and normally does not touch the ground in walking. It has 

 only two phalanges, while each of the other digits has three. 

 A pair of small sesamoid bones are developed on the ventral or 

 fiexor side of the metacarpo-phalangeal articulations of all the 

 digits except the pollex. Frequently similar sesamoid bones 

 occur also on the dorsal side of the phalangeal articulations. 



THE PELVIC GIRDLE. 



The pelvic girdle consists of two halves, which lie nearly 

 parallel to the vertebral column. 



Each half is firmly united to its fellow in a ventral 

 symphysis behind, and is in front expanded and united to the 

 sacrum. Each half or innominate bone is seen in the young 

 animal to consist of four distinct parts, the ilium or dorsal 

 element, the pubis or anterior ventral element, the ischium 

 or posterior ventral element, and a small fourth part, the 

 acetabular or cotyloid bone, wedged in between the three 

 others. These parts, though all distinct in the young animal, 

 are in the adult so completely fused that their respective 

 boundaries cannot be distinguished. At about the middle of 

 the outer surface of the innominate bone is a very deep cavity, 

 the acetabulum (fig. 78, A, 1) with which the head of the 

 femur articulates ; all the bones except the pubis take part 

 in its formation. 



The ilium is a rather long bone, expanded in front and 

 contracted behind ; it forms about half the acetabulum. On 

 its inner or sacral surface (fig. 78, 4) is a large roughened 



