ii 



of the head of the thigh-bone, making together a ball and socket-joint 

 6f great strength, from whence these tvvo bony columns proceed to the 

 ground in a direction nearly parallel, not converging, as the fore limbs do, 

 their forces are thus more strongly directed upon the mass they have to 

 transport, the frame of the pelvis rcceiving their impression and con- 

 Vcying it to the trunk. The thigh-bone, articulated nearly at the same level 

 as the point of libration of tlie scapula, which is somewhat higher than its 

 middle. The thigh is very similarly situated, between the column of the 

 limb and ilium, as the arm in the fore extremity, reversed however in its 

 direction, and advancing forwards to the stifle, as that does backwards to 

 the elbow, and it describes in the ränge of its action a much greater portion 

 ofacircle passing in strong movement even behind a perpendicular line 

 falling from the acetabulum, thus powerfully forcing forwards the body. 

 The rest of the limb is divided into similar parts to the fore extremity, but 

 with angles more acute. 



I observed, in frequently dissecting this limb, in the years 1791-2, at the 

 Veterinary College, a singular Variation of structure between the horse and 

 the smaller animals, which seems worth recording : the horse appears to be 

 driven forward almost by the limbs alone, while the dog and other small 

 animals, which in comparative swiftness exceed the larger, effect their 

 speed more by the. muscies of the back, some of which are inserted into 

 the inside of the ilium in rather an extraordinary way, acting there with 

 great power upon the line of the spine ; this circumstance appears to be 

 overlooked by Douglas in the Myologia Comparata, though expressly on 

 the anatomy of the dog: in the horse this part of the ilium is occupied by 

 the muscies of the thigh, and it is perhaps the rigidity arising from the mag- 

 nitude of the spine in large animals, which renders this principle incom- 

 patible or inconvenient, and is the cause of its not being pursued. In 

 observing the bind legs of animals, it may be presumed, with tolerable 

 certainty, whether speed or strength is designed to prevail, and in what 

 degree, by the acuteness of their angles and the length of the limb : thus the 

 bind limb of the elephant is nearly a straight column ; and the leg of the 

 dog is crooked to a proXverb. ■Ij ,.) noii - 



A limb detached from the trunk with its apparatus of ifiuscles makes 



the 



