48 THE HORSE IN MOTION. 



the patella to play on as over a pulley ; the tendon of the triceps, after 

 being inserted into the patella, is extended beyond it to be inserted into 

 a rough tubercle in the head of the tibia. Anatomists call the portion 

 below the patella, ligament. Physiologists may say that the patella is 

 developed in the tendon. We will not discuss the question. It is to 

 us as if the bone was developed in the tendon as it is developed in ten- 

 dinous fibres elsewhere, and the ligament below the patella does the 

 same ofifice as the tendon above. The force of this powerful muscle 

 as determined by its circumference can only be compared to the great 

 gluteus, and is called into action after the extreme of flexion has been 

 passed, and the femur has been brought forward by its flexors already 

 referred to, and in which the rectus may have borne a part. After the 

 foot has taken the ground it steadies the stifle, or knee, and regulates 

 the flexion of that joint as the angles close to shorten the limb. After 

 the perpendicular is passed, it again resumes the offensive and extends 

 the leg in giving the propulsive impulse, which it maintains to the 

 close of the stride. It rests, therefore, but for one fourth of a stride, 

 and if the rectus acts as a flexor of the thigh at the same time with 

 the flexors of the thigh upon the pelvis it has but little rest. 



The gastrocnemii {Plate VIII., m, m), or superficial muscles of the 

 calf, hold a corresponding position on the leg to that of the triceps on 

 the thigh, as well as to the levers on which they act ; but while the 

 action of the triceps is very simple and easily comprehended, that of 

 the muscles of the calf is very complicated, and can only be understood 

 by a study of the whole limb as a machine of which the voluntary 

 muscles form a part. Whetlier it will be possible for me to interpret 

 the action of the muscles and the use of the tendons with their checks 

 and reinforcements without the actual limb before us is a question to 

 be determined. An attempt was made to represent the parts by the 

 aid of the camera, but the results were not satisfactory. Plate X. is 

 from a careful drawing by Hahn. The gastrocnemius of the right side, 

 g, is dissected away from its origin in the femur and raised by hooks 

 to show the perforatus tendon,/. This tendon is inserted into the 

 femur about two inches from the joint, along with the gastrocnemii 

 muscles. It has a muscular body of its own, not distinguishable in 



