58 FORM AND ACTION. 



trunk is solely through muscles ; and that in the horse, as in most 

 quadrupeds, the speed results from the strength of the loins and 

 hinder extremities, Sir Charles continues, " Were the anterior ex- 

 tremities joined to the trunk firmly, and by bone, they could not 

 withstand the shock from the descent of the whole weight thrown 

 forwards; even though they were as powerful as the posterior ex- 

 tremities, they would suffer fracture or dislocation. We cannot 

 but admire, therefore, the provision in all quadrupeds whose speed 

 is great, and whose spring is extensive, that, from the relative po- 

 sition of their bones, they have an elastic resistance, by which the 

 shock of descending is diminished." 



" If we observe the bones of the anterior extremities of the 

 horse, we shall see that the scapula is oblique to the chest; the 

 humerus oblique to the scapula; and the bones of the fore-arm, 

 (called by us the arm) at an angle with the humerus. Were these 

 bones connected together in a straight line, end to end, the shock 

 of alighting would be conveyed through a solid column, and the 

 bones of the foot or the joints would suffer from the concussion. 

 When the rider is thrown forwards on his hands, and more cer- 

 tainly when he is pitched on his shoulder, the collar-bone is broken, 

 because, in man, the bone forms a link of connexion between the 

 shoulder and the trunk, so as to receive the whole shock ; and the 

 same would happen in the horse, the stag, and all quadrupeds of 

 great strength and swiftness, were not the scapula sustained by 

 muscles, and not by bone, and did not the bones recoil and 

 fold up." — " Much of the strength, if not the freedom and rapidity 

 of motion, of a limb, will depend on the angle at which the bones 

 lie to each other ; for this mainly affects the insertion, and, con- 

 sequently, the power of the muscles. We know, and every 

 moment feel, that when the arm is extended we possess little 

 power in bending it ; but as we bend it the power is increased, 

 which is owing to the change in the direction of the force acting 

 upon the bone, or, in other words, because the tendon becomes 

 more perpendicular to the lever." 



We have already shewn that the scapula possesses a rotatory 

 sort of motion upon the ribs, and that the sphere of its motion be- 

 comes increased by its degree of obliquity. Sir C. Bell has ex- 

 plained the cause of this — " the serratus muscle" — the fleshy at- 



