lo STRUCTURES OF THE BODY. 



nerves, to the biceps muscle, which is attached at one end to 

 the shoulder-blade, close to the shoulder-joint, and, at the 

 other, to the bones of the fore arm, a little below the elbow. 

 Hence this muscle, on contracting, draws the hand up in the 

 required direction. 



As muscles are built up of contractile fibres, their 

 strength, other things being equal, is proportionate to their 

 thickness. 



In order to economise space, muscles are generally- 

 attached to bones by means of tendons (sinews), which are 

 hard, fibrous cords of great toughness. The tendon at one 

 extremity is firmly united -to the end of the muscle, and, 

 at the other, to the bone. 



We find from experiment that a muscle can contract to 

 about two-thirds of its ordinary length, which is, therefore, 

 proportionate to the extent of movement it is capable of 

 producing. If the muscles which move the limbs be com- 

 paratively short, .he stride will also be short, and the 

 horse will be slower than he would otherwise be, no matter 

 how thick and powerful are his muscles. We may, there- 

 fore, conclude that speed is associated 'with length of 

 muscle, as has been stated on page 4. 



As length of muscle is necessarily accompanied by 

 length of bone, we may judge of the former by the latter, 

 which can usually be readily estimated. 



The *'give and take" principle, which applies more or 

 less to all created things, holds good with muscles. Hence, 

 in the race-horse, for which the possession of speed is the 

 chief essential of success, we should seek the greatest 

 possible length of muscle, with just sufficient strength to meet 

 his requirements for carrying weight and for sustaining the 

 exertion he may be called upon to undergo. In the cart-horse, 

 on the contrary, thickness of muscle is the great desideratum, 

 always supposing that he has sufficient activity to walk well 

 and on occasion to trot at a moderately brisk rate. As a thin 

 muscle will contract at least as quickly as a thick one of the 

 same length, it follows that an increase in the thickness of 



