360 THE MECHANICAL FUNCTIONS. 



iiectiiig bones of the posterior extremity are three 

 in number, and constitute, together with the part 

 of the spine to which they are attached, what is 

 called the Pelvis (p). The part of the spine which 

 is thus included in the pelvis, is termed the Sacrum. 

 In its complete state of ossification it is a single 

 bone ; but it was originally composed of a number 

 of separate vertebrae, which have afterwards become 

 consolidated into a single bone, and whicii bear the 

 marks of having been compressed from behind for- 

 wards during their growth, so that they could only 

 expand laterally. The vertebrae which succeed to 

 these, and which are not consolidated with the 

 sacrum, compose what is called the os coccygis. (q), 

 or more properly the coccygeal vertebrce : when they 

 are sufficiently numerous to compose a tail, they 

 come under the denomination of caudal vertebrce. 

 The three bones of the pelvis, are the ilium, the 

 ischium, and the pubis. They all concur in the 

 formation of a large cup-like cavity, called the ace- 

 tabulum, which receives the round head of the thigh 

 bone (f), and constitutes generally the largest joint 

 in the body. 



A single bone composes the first division of each 

 limb, both in the fore and hind extremities. In 

 the foreleg it is termed the humerus (u), in the hind 

 leg, the femur (f.) The next division contains two 

 bones, placed parallel to each other ; they are in 

 the formerj the radius (r), and the ulma (u) ; in the 

 latter, the tibia (t), and fibula (f). These are fol- 

 lowed by a number of small, rounded or cubical 

 bones, collected together in a group, which consti- 

 tutes the Carpus (w), in the fore leg, and the 2\ir- 

 us (t), in the hind leg. Next come a set of long 



