108 FORM AND ACTION. 



through the means of their joints, moving upon each other, to that 

 extent and in that direction, which is needed for the action of the 

 parts ; and the muscles or acting powers superadded to it, are so 

 applied and distributed upon it, that, while they are enabled to 

 move every part in the manner it was designed to move, they, so 

 far from encumbering or disfiguring the frame-work, confer upon 

 it beauty of form and handsome exterior. It is true that the mus- 

 cles might have been placed greatly more to their advantage as 

 moving powers ; but in such case not only must outward appear- 

 ances have been sacrificed, but the form of the animal would have 

 turned out such as would have materially interfered with his present 

 functions and uses : thus what he had gained in power he would 

 have more than lost in inaptitude and encumbrance. 



The bones, in their figure and in the construction of their joints, 

 offer every facility compatible with the general form of the animal, 

 to the agency of the muscles, the power of the latter depending 

 upon that facility, which is greater in some subjects than in others, 

 and upon their own magnitude and texture. The principle upon 

 which movement is effected is that of the mechanical power of the 

 lever — the greater the leverage presented by the bones, the greater 

 the effect of the action of the muscle upon it ; and as muscles, gene- 

 rally speaking, possess power commensurate with their size, the 

 larger the muscle the greater its power of contraction or action. 

 These are the two leading principles on which depend the powers or 

 strength of an animal ; there is a third, also to be taken into con- 

 sideration, which is the texture of the muscle, the quality of its 

 fibre or component parts. That horse whose bones are so formed 

 and arranged as to offer the longest or most advantageous levers, 

 will, cceteris paribus, prove the strongest or most powerful : sup- 

 posing, however, his muscles to be deficient in power, from want- 

 ing bulk, or from being lax or adulterated in composition, his 

 length of lever will prove of little profit to him. The same may 

 be said in cases where the muscles are powerful, but the leverage 

 short or upright, and consequently disadvantageous. 



In the course of our investigation into the quality of bone in 

 horses of different breeds or kinds, we detected a manifold differ- 

 ence between the solidity and texture of the bone of the cart-horse 

 and that of the race-horse ; and if we prosecute our inquiries still 



