180 PROCEEDINGS OF THE ACADEMY OF [1894. 



biceps is to extend the scapula on the humerus. This extension of 

 the scapula pulls through the triceps on the olecranon, and thus gives 

 the biceps a longer leverage on the radius than its own tendon gives it 

 in front of the elbow joint. Consequently the biceps extending the 

 scapula also extends, not flexes, the radius. 



The long head of the triceps, with its long leverage on the olecra- 

 non, extends the forearm, but in so doing it pulls on the tendon of the 

 biceps which, with its short leverage below and long leverage above, 

 extends the shoulder joint, notwithstanding the direct insertion of the 

 triceps into the scapula. The simultaneous contraction of the two 

 muscles will raise the shoulder-blade above the tendinous trajectory, in 

 replacing the tendons and aponeuroses by shorter lines. This causes, 

 especially towards the end of the stride, the great diff^erence between 

 the trajectories oi the dead and the living horse. Other circuits of 

 strains connect this part of the limb with the lower part and others 

 with the trunk, so that the least action anywhere is carried through 

 the whole animal. The differential action of the muscles secures to 

 the scapula from which the horse's body hangs, a much longer and 

 swifter throw, a concurrent and auxiliary movement of great mus- 

 cles, generally supposed to be antagonistic, a grace and harmony that 

 any less perfect system of co-ordination would surely miss. This 

 differential scheme is, perhaps, more apparent in the limbs of the 

 horse than anywhere else, but it extends to other parts of its muscular 

 system and to that of other animals including man. 



I think these differential muscles have been a great obstacle to 

 study. One is never sure that he understands the least movement of 

 an animal, unless he can connect it with the whole muscular system, 

 making, in fact, a complete circuit of all the strains. The differential 

 muscles once understood, it is less difficult to connect nearly all the 

 other great muscles with the principal movement of the animal, that 

 of progression in the horse; and to understand, roughly, the com- 

 binations necessary for other movements. 



On the lines of the mighty and simple strains dominating the move- 

 ment, and felt intuitively and studied out by him, the master artist 

 groups, with full intention, his muscular forms. No detail contra- 

 dicts. His men and animals live. Such is the work of three or 

 four modern artists. Such was the work of many an old Greek 

 sculptor. 



