MUSCLES AND TENDONS. 27 



rapid progression. Hence we find that the race-horse, 

 like all quadrnpeds of which speed is the chief character- 

 istic, has comparatively slender bones of extremely dense 

 texture, and that his muscles are particularly strong 

 for their thickness. Owing to the law of compensation, 

 which governs the conditions of animal life, it is almost 

 impossible to obtain bone of great volume, and, at the 

 same time, of the finest quality. On this account, as 

 weight is indispensable in the cart-horse, we endeavour, 

 with him, to obtain large bone of sufficient strength to 

 meet his requirements. In the intermediate classes of 

 horses, the relations between volume and quality should 

 be judged according to the nature of the work in \dew. 



Arrangement of bones. — The relative position which 

 bones occupy with respect to each other, affect their 

 leverage, weight-carrying, and concussion-resisting powers 

 — conditions which will be treated in detail when the 

 various points which they affect are considered. 



Cartilage. — Cartilage or gristle is a strong, flexible, 

 bluish-white substance which is found in connection 

 with bone, and of which there are various kinds. 

 Articular cartilage covers the ends of bones that form 

 movable joints. Temporary cartilage is bone in a tran- 

 sition form. The ribs are connected to the breast-bone 

 by cartilages which form elastic prolongations. Cartilages 

 also are interposed between the bones of various joints 

 in order to connect or protect them. The cartilage of 

 prolongation forms an elastic continuation of the top of 

 the shoulder-blade. 



Muscles and Tendons. — The animal's moving 

 power is deri\'ed from )iinscles, which form the lean of 

 meat, and w-hich, as a rule, are attached to bones. 

 Muscles act by virtue of the property they possess of being 

 able to shorten themselves on being stimulated by the 

 nervous system. Thus, if we wish to raise, say, our right 



