ANATOMICAL CONSIDERATIONS. 39 



very limited movement, the wliole is gifted with an evident elasticity 

 which affords an easy seat to the rider. 



THE SPINE OF THE HOBSE, OE THE BASIS OE ITS ANATOMICAL FRAMEWOEK. 



Along the top of the back-bone runs a strong cord of yellow, elastic 

 fiber, which unites the several parts, holding these firmly together as one 

 whole. The elastic cord, however, passes directly from the last dorsal 

 spine, to be fixed into the back portion of the skull, thus skipping over 

 all the bones of the neck. The fibers of this cord are longitudinally 

 arranged ; and however elastic such a substance may be, the dorsal 

 arrangement would not allow of that freedom of motion which was 

 requisite in the neck of an animal which was to crop its food from the 

 surface of the earth. 



The necessity, however, was fully met by an elastic cloth being, as it 

 were, thrown over the cord, and extending thence to the bones of the 

 neck. By this arrangement, frequent attachments were avoided and 

 grace of outline was preserved, while no deterioration was made in that 

 provision by means of which the heavy head is supported without ap- 

 parent strain upon the muscular fiber. One end of the elastic expansion 

 being inserted into the cervical bones, all the ease and beauty of move- 

 ment is rendered* possible by the retractile property of the cloth-like liga- 

 ment being fully equal to the sustenance of the weight, but not strong 

 enough to resist the action of the muscles when excited. Thus, the 

 muscles situated at the base of the neck serve to depress the head ; the 

 elastic cloth answers as a counterpoising force, which steadies the move- 

 ment ; the action of the motor agents near the crest, aided by the liga- 

 mentous elasticity of the neck, serve to elevate the part, while the mus- 

 cular power at the base of the bones regulates and guides the upward 

 motion. 



But the reader may be desirous to learn how far the back of the animal 

 is suited to endure the weight of the rider. The bones of the spine, not 



