THE ANATOMY OF THE HORSE 



41 



Fig. 22. — Superficial muscles of the horse. "Muscles differ in length and 

 strength." (Courtesy Dr. S. Sisson. Reproduced from Anatomy of the 

 Domestic Animals.) 



tract to aboitt two thirds its ordinary length if conditions 

 favor the same. The power of a muscle is in accordance 

 with its thickness, while its action is dependent on its 

 length. Comparatively the draft horse with a thick, short 

 muscle, moves slowly and in short powerful strides, while 

 the race horse, with long muscles possesses a longer stride 

 and covers ground more rapidly. Muscles of the same size 

 on different animals vary in strength, this being due to 

 heredity, food, condition, nervous power, etc. "Massive 

 muscles," says Hayes, ^ "compared to slight ones, have two 

 disadvantages, namely, — they increase the weight which 

 is carried, both in muscle and bone; and they necessitate 

 the possession of large joints, which from increased friction, 

 are not so easily bent and extended as smaller ones ; besides, 

 it has been proved that they do not respond as quickly to 

 nervous stimulus." Hayes makes the further interesting 

 observation that we may often note that race horses which 

 were very smart as two-year olds, lose their "form" after 

 that age without any assignable reason, excepting that as 



^ Points of the Horse. M. H. Hayes, London, 3d ed., 1904, p. 29. 



