REGULATION OF THE CENTRE OF GRAVITY, 71 



the reins remains unaltered, should be advanced, as may be 

 required; if it be decreased, they should be drawn back. 

 Thus, any alteration by the rider, of tension on the reins 

 which might impede the legitimate movements of the neck, 

 is avoided. As the joint which the head makes with the 

 atlas (first vertebra of the neck) is situated some distance 

 below the top of the head, it follows that if the muzzle 

 be unduly stretched out, the occipital crest (top of the 

 head) will be brought back, and the tension of the liga- 

 ment of the neck lessened, with consequent decrease of 

 power to the muscles which are attached to this ligament. 

 The muscle which is attached to the humerus and top of the 

 head, also would work to disadvantage if the muzzle were 

 stretched out to a greater extent than would bring the 

 line of the face to a right angle with the direction of this 

 muscle, which forms the upper border of the jugular 

 groove. Even in the fast gallop {vide Figs. 133 to 148), the 

 horse rarely carries his head at a less angle than 45° to 

 the ground, 



(3) To regulate the position of the Centre of Gravity. — 

 The more the head is advanced to the front, the more 

 unstable will be the equilibrium, and the greater will be 

 the speed during progression (p. 54). Hence, the race- 

 horse, when galloping at full speed, will bring his head 

 forward as much as the other conditions which affect its 

 carriage will allow him to do. As I have before remarked, 

 the angle which his face makes with the ground will 

 seldom be less, even at the highest speed, than 45"". The 

 cart-horse, if he has good foot-hold, will also, when pulling 

 a heavy load, lower his head and stretch it out, so as to 

 bring the centre of gravity forward as much as possible. 

 Here I assume that the ground is soft enough to allow 

 him to *Mig his toes" into it, or, if it be rough, that he 

 is provided with toe-pieces on his front shoes. If, on the 

 contrary, the roadway is slippery, like the London streets 

 which are covered with asphalte or wood, the cart-horse 

 in heavy draught, being afraid of falling down if he throws 



