THE HORSE IN MOTION. 51 



converts the part below it into a continuous tendon, which performs 

 the office of a ligament, in common with that of the perforatus, to 

 aid the suspensory ligament in supporting the weight of the body in 

 the extreme extension which the pastern undergoes when the centre 

 of gravity is over it, as in rapid locomotion. 



Muscular fibres are found by anatomists scattered through the 

 tendons below the hock ; but for all mechanical purposes the sources 

 of power are above and away from the extremities, where the velocities 

 are, at times, more than twice that of the body and the momentum 

 must be arrested at every stride. The hock in quadrupeds represents 

 the heel in man, and the elongations of bones and corresponding 

 tendons are necessary modifications of the plan for the development 

 of speed. 



There is a group of small muscles which form what is called, by 

 some horsemen, the second thigh ; they are on the outer face of the 

 thigh and below the stifle, or knee, and in front of the calf. The 

 perforans (d, Plate X.) is in this group, occupying the intermediate 

 place. 



The flexor of the metatarsus has its upper attachment on the 

 tibia, in front of the perforans, and its lower in the metatarsus, below 

 the joint, after passing under the annular ligament. It is minutely 

 described by Chauveau. It flexes the hock joint and is a feeble an- 

 tagonist to the gastrocnemii, but only acts when the foot is off the 

 ground. 



The lateral and anterior extensors occupy, as their names indicate, 

 spaces on the tibia in front of the latter, and their tendons, after passing 

 under the annular ligament, in front of the hock, descend to be in- 

 serted into the anterior face of the foot ; they act, therefore, to flex the 

 hock and extend the foot, raising the toe as the limb is thrust forward 

 to take the ground. 



The suspensory ligament is one of the most wonderful contrivances 

 in the whole locomotive machinery of the horse. Though a ligament 

 only, with its action beyond the control of the will, it is no less an active 

 organ, whose function is indispensable to locomotion, and the interest 

 in it has been much increased by the developments of the camera. 



