MUSCLE 253 



animal and improve the conformation and qualities of feet 

 and legs. The former has improved in Shires and the 

 latter in Clydesdales. 



The force that a horse can extend on a steady pull has 

 been found by F, Smith to be about 75 per cent, of its 

 body weight. The load which can be pulled depends largely 

 on the condition of the road and the nature of the vehicle. 

 On a level road a total weiglit — vehicle plus load — of 2-5 

 to 4-5 times the weight of the animal can be pulled at a 

 walking jDace. 



On a rising gradient, in addition to the pull to overcome 

 the inertia of the load on starting and the friction in motion, 

 the load and the animal itself must be raised against gravity. 

 The load that can be drawn up-hill therefore decreases very 

 rapidly as the gradient rises. 



As the co-ordination of muscle of two or more horses 

 pulling together is not so perfect as that of a single animal, 

 the amount that can be pulled by more than one horse is 

 always less than the sum of the amounts each can pull 

 separately. 



Carrying. — The horizontal spine of the horse is not 

 adapted for carrying weights. About one-fifth of the body 

 weight is the maximum load a horse can carry comfortably 

 for any length of time. In this respect it is less efficient 

 than man \nth his vertical spine. An infantry soldier can 

 march carrying more than a third of his weight. The 

 smaller breeds of horse can carry more in proportion to 

 their weights than the larger. Consequently a nuile or pony 

 is a more efficient pack animal than a large horse. 



Over-work. — -A horse that is worked beyond its capacity 

 rapidly deteriorates and is liable to injury of the feet and 

 legs caused by excessive strain. When the muscles are 

 tired undue strain is allowed to fall upon the supportino- 

 tendons Avhich become injured. Co-ordination of tired 

 muscle is less perfect, and " brushing " and stumbling occur. 

 Severe work, necessitating a propulsive force as in heavy^ 

 draught, or concussion as in high speed, greater than the 

 elasticity of the structures of the foot can accommodate, is 

 apt to injure the matrix and produce laminitis. Horses 



