620 



COMPARATIVE PHYSIOLOGY. 



The advantages of such an ar- 

 rangement, to an animal in which 

 a great deal of forward-pitching 

 movement occurs, in breaking 

 shocks are evident. The length- 

 ened metatarsals and phalanges 

 are accompanied by a very per- 

 fect bracing of joints by liga- 

 ments and tendons below, while 

 the shoulder is strengthened and 

 bound to the trunk by numerous 

 muscles, so that the whole, in 

 neatness, strength, and other 

 qualities required in a fleet ani- 

 mal, is, especially when taken in 

 connection with the feet, an ex- 

 ample of marvelous adaptation 

 to conditions to be constantly 

 met, aided in the wild species by 

 natural selection, and in our do- 

 mestic varieties by artificial se- 

 lection. 



An examination of Fig. 470 

 will show the several levers 

 (bones) and the muscles acting on 

 them in one main movement of 

 the fore-limb. 



The hind-limbs are in all gaits 

 of theanimal its main propellers, 

 and these are in bony connection 

 with the pelvis. 



Pig. 469. — External muscles of right anterior 

 limb (Clianveau). 1, 1, long abdactor of 

 arm; 1', its humeral insertion: 2, super- 

 spinatus ; 3, sabspinatas; 3', its tendon 

 or insertion ; 4, short abductor of arm; 

 5, biceps; 6, anterior brachialis; 7, large 

 extensor of forearm; 8, short extensor 

 of forearm; 9, anconeus; 11, anterior ex- 

 tensor of metacarpus; 11', its tendon; 13, 

 aponeurosis, se^parating that muscle from 

 anterior brachialis; 13, oblique extensor 

 of metacarpus ; 14, anterior extensor of 

 phalanges; 14', its principal tendon; 15, small tendinous branch it furnishes to 

 lateral extensor; 16, lateral extensor of phalanges; 16', its tendon; 17, fibrous 

 band it receives from carpus; 18, external flexor of metacarpus; 19, its metacar- 

 pal tendon; SO, its supracarpal tendon; 21, ulnar portion of perforans; 28, tendon 

 of perforans; 23, its carpal ligament; 24, its re-enforcing phalangeal sheath; 25, 

 tendon of the perforans. 



