to pelvis, lie the great muscles which move the fore and hind limbs, and which are the principal agents in locomotion. Of these the latissimus dorsi carries the arm upward and backward, the longissimus dorsi, when it acts alone, is a powerful extensor of the vertebral column, and the deep pectoralis, attached at the angle of the shoulder, draws the whole fore limb backward. The student desiring to understand more fully the attachments, relations, and actions which are effected by pressure of the rider's legs, should consult some standard work on the anatomy of the horse.
It is, then, easy to understand that the rider's legs affect first of all the horse's hair, skin, panniculus carnosus, and abdominal tunic, all of which have nothing to do with locomotion; while the great pectoralis and its adjuncts, the latissimus dorsi, and the muscles of the haunches and hind limbs, are either affected only secondarily or remain unimpressed. But the first contact of the rider's legs is for the horse rather unpleasant than otherwise. It takes, therefore, patient teaching to accustom the untrained animal to endure this contact without anxiety, nervousness, or fear. Only after the horse, standing quiet and calm, supports the pressure of the legs on all parts of the body, from as far forward as the rider can reach to as far backward, has the time come for teaching the significance of this contact for the more important muscles of locomotion, such as the great pectoralis.
