282 THE MECHANICAL FUNCTIONS. 



ischhim, and the pubis. They all concur in the formation 

 of a large cup-like cavity, called the aceiabidum, which 

 receives the head of the thigh bone (r,) constituting, gene- 

 rally, 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 fore leg it is 

 termed the humerus (n,) in the hind leg, the femur (f.) 

 The next division contains two bones, placed parallel to each 

 other; they are, in the former, the radius (r,) and the ulna 

 (u;) in the latter, the tibia (t,) and fibula (f.) These are 

 followed by a number of small, rounded, or cubical bones, 

 collected together in a group, which constitutes the Carpus 

 (w,) in the fore leg, and the Tarsus (t,) in the hind leg. 

 Next come a set of long cylindrical bones, composing the 

 metacarpus (m,) in the former, and the metatarsus (m,) in 

 the latter case. In the most complete forms of development, 

 these are always five in number, in each limb; they are 

 placed generally parallel to each other, but are enveloped in 

 one common covering of integument. The Phalanges, or 

 toes (z,) are cylindrical bones, continued in a line from each 

 of the former: they are generally three in number in each 

 toe. To the last joint, which is often termed the ungual 

 bone, there is usually attached either a nail, a claw, or a 

 hoof. Small, detached bones are frequently found at the ex- 

 terior part of the angles which they form by their junction, 

 serving the purpose of giving a more advantageous position 

 to the tendons of tl\e muscles which extend those joints. 

 i:he patella, or knee pan (k,) is the largest of these, and is 

 pretty constantly present. Smaller bones of this description 

 are met with on the joints of the fingers, and are termed ^e- 

 samoid bones. 



On comparing these divisions of the limbs of quadrupeds 

 with those of insects, we cannot fail to perceive that there 

 exists between them a marked analogy; and that naturalists 

 were not led away by mere fancy when they applied to the 

 latter the same names as those borne by the former. This, 

 however, is not the only instance of analogy that may be 

 discovered between the structures of articulated and of ver- 



