HORSESHOEING. 75 



larly and meet the ground first with the toe; however, careful 

 observation will detect the presence of one or the other of these 

 lines of flight of the foot. Irregular carriage of the feet renders 

 a horse unsuitable for general purposes only when it is very 

 pronounced, in which case certain troublesome conditions, such 

 as interfering and disease of joints, are of frequent occurrence. 



D. The Influence of Weight in the Shoe or Otherwise Attached 

 to the Hoof, in Altering the Flight of the Hoof. 



There is nothing mysterious in the effect of weight upon 

 the flight of the feet. On the contrary, the lines of flight are 

 determined (as shown in pages Y2-74, Figs. 71-76), first, by 

 the relation of the transverse axes of the hinge-joints of tJie 

 leg and foot to the line of progression (median line) ; second, 

 by the length and obliquity of the hoof and pastern ; third, by 

 the height and length of stride which is natural to each in- 

 dividual. 



Weight induces higher action and a longer stride. Inertia 

 increases with the weight. A heavy shoe cannot be snatched 

 from the ground as quickly as a light one, but when moving 

 forward at a given velocity its greater momentum ( momentum = 

 mass (wt) X velocity : m = wt X v) carries the foot farther 

 forward than does the lighter shoe. Thus, the heavier shoe, 

 or M^eight attached to the hoof, lengthens the stride at both ends. 

 The farther from the centre of rotation of the scapula the 

 weight is placed, i.e., the nearer to the toe it is placed, the 

 greater the muscular effort required to start it and to stop it. 



Height of action, though largely the result of breeding, 

 temperament, and the exhilaration that accompanies perfect 

 health and entire absence of muscular fatigue, is to a certain 

 extent influenced by the inclination of the pastern and toe to 

 the camion. The acute-angled foot, in the folding of the leg 

 during the first half of the stride, moves through a longer arc 

 of a circle whose centre is the fetlock joint than does the normal 

 or the upright foot ; rises more rapidly and to a higher point. 



