SPECIAL FEATURES IN STRUCTURE 487 



possible in tlie elbow-joint of man, while in the horse, owing to the rudi- 

 mentary form of the second bone of the arm {the ulna), no lateral or rotatory 

 motion can take place. The movement is purely hinge-like. 



Another marked peculiarity is observed in tlie connection of the shoulder- 

 blade (scapula) with the trunk. In man the junction is effected by a bone 

 known as the collar-bone (or clavicle), wliich extends from the shoulder- 

 bone near the shoulder-joint to the first rib on each side. The horse has 

 no vestige of a collar-bone; the shoulder-blade (scapula) is joined to the 

 trunk only by means of the muscles which are attached to it, so that the 

 fore part of the horse's body is suspended by the aid of muscular bands 

 between the two fore -legs. 



An examination of the hinder limbs will show that the general plan of 

 construction is nearly the same in both man and horse, as far as the joints 

 ai-e concerned. The hip-joint, the stifle (the true knee) with tlie floating 

 bone or knee-cap (jjatella), and the hock (ankle of man) are almost identical 

 in mechanical arrangement. 



With regard to the hock-joint it may be observed that the two rows of 

 small bones are placed as in the ankle of man, but the movement of the 

 joint is purely hinge-like, and experience proves that the two rows of small 

 bones may be cemented together, and to the cannon-bones and splint-bones 

 below them, by bony deposits in old horses without causing any defect 

 in the action — to a sufficient extent, at least, to be noticed. In fact, the 

 provision for perfectly complete flexion in the hock-joint is secured by the 

 mode of junction of the bones called tibia and astragalus (see fig. 658). 

 The so-called cushion bones do not appear to contribute much, if anything, 

 to the mobility of the joint, in the flexion and extension of which the small 

 bones are largely concerned. 



Below the knee in front, and the hock behind, begins the hand and foot 

 respectively. The one large digit in each extremity, comj^osed of what are 

 called the metacarpal and metatarscd bones; the rudimentary second and 

 fourth digits (the splint-bones) attached to them, and reaching two-thirds 

 of their length, and the three following phalanges, constitute the true liand 

 and foot. The horse, in fact, stands on those parts which in man form 

 respectively the tip of the middle finger and the point of the middle toe, 

 both of which are capped with an investing hoof instead of a nail. 



The next illustration shows the exact relation between the finger of man 

 and the reputed foot of the horse. How very close the anatomical relation 

 is will be at once evident. 



The chief anatomical difference between the fingers of man and the foot 

 of the horse (which represents the end of the middle finger) consists in the 

 presence of — (l) a complete horny box or hoof, which covers the organ in 



