OSTEOLOGY AND ARTHROLOGY 75 



mettle which leaps over an elevated obstacle, the animal 

 forcibly raises his fore-limbs by flexing them. Flexion is 

 produced to the same extent, and even more so, and for a 

 longer period, in felides which crouch. 



In extension, on the contrary, the forearm is carried back- 

 ward. This movement being limited only by the contact of 

 the tip of the olecranon with the bottom of the olecranon 

 fossa of the humerus, the forearm is enabled, in this case, to 

 move until it is in line with the arm. For example, during 

 walking, when one of the anterior limbs, having reached the 

 end of its resting stage, is considerably inclined downwards 

 and backwards. 



The apex of the olecranon process — that is to say, the point 

 of the elbow — forms a marked prominence, more salient in 

 flexion than in extension, as in the corresponding region of 

 the human elbow. 



The Radio-ulnar Articulation. — It is in the dog and 

 the cat, in which the two bones of the forearm articulate by 

 their extremities only, and remain separate in the rest of 

 their extent, that the articulations call for special notice. 



In the upper part, the radius rotates on itself ; while 

 below, it rotates around the ulna. It follows that the fore- 

 arm, which in all quadrupeds is in a state of permanent 

 pronation, can, in carnivora, take the position of supination, 

 or rather, of demi-supination. In fact, whatever be the 

 mobility of the two bones of the forearm, the movement is 

 not able to bring the palmar surface to the front, but only to 

 direct it towards the median line. 



The Articulation of the Wrist. — Here are found, as in 

 man, three superimposed articulations : the radio-carpal, 

 intercarpal, and carpo-metacarpal. 



If we remember the movements which take place at the 

 plane of these articulations in man, and take account of the 

 fact that the mobility of the limbs is reduced just in proportion 

 as they are simplified in structure so as to become organs of 

 support only, we can easily comprehend that, in the horse and 

 the ox, and, in a word, animals that have a canon bone, the 

 movements of the wrist are little varied in character, while 

 in carnivorce, on the other hand, they are relatively more so. 



