THE SKELETON. 251 



time it serves tlie purpose of locomotion. In both these divisions 

 of the animal kitigdom the skeleton forms a series of arches or 

 rings, capable of moving on each other, but so firmly attached as 

 to secure protection to the important organs contained within them. 

 In the horse, as in all the higher mammalia, these rings or arches 

 are double — one set, the superior, being continuous throughout the 

 whole length of the animal from the head to the root of the tail, 

 and containing the nervous system ; while the other lying below, 

 but closely connected to them, is interrupted in certain localities, 

 being found to exist chiefly in three regions : — 1st, where it forms 

 the jaws and bone of the tongue ; 2d, where, by means of the ribs 

 and sternum, it constitutes the thorax and its appendages, the an- 

 terior extremities ; and, thirdly'-, where, in the shape of the pelvic 

 arch, it protects the organs of generation, and, through the poste- 

 rior extremities prolonged from it, assists in locomotion. The 

 superior of these arches, from containing the brain, and its pro- 

 longation, the spinal cord, is called the neural arch. The inferior 

 is termed the hsemal arch (al//.a, blood), because it protects the 

 heart and its large blood-vessels as the latter pass from the thorax 

 towards the head and posterior extremities. In all the vertebrata 

 the neural arch consists of one continuous cavity, defended from 

 end to end by bony plates, strongly joined together; and in some 

 of the lower forms (lizards) the haemal arch is nearly as complete, 

 these animals having cervical ribs ; while the dugong and some 

 others are furnished with ribs in their tails. Consequently, it is 

 fair to consider the whole skeleton in the superior forms of the 

 animal kingdom as composed of two series of arched plates, firmly 

 united together, but still allowing more or less motion, and serving 

 to protect the centres of the nervous and sanguineous systems, 

 from which they have received their names. 



THE ARTIFICIAL SKELETON. 



The bones of the Horse, as of the other mammalia, may be 

 preserved with their natural ligamentous attachments connecting 

 them in a dry state, in which condition the skeleton is called a 

 natural one. It is usual, however, to macerate them so long that 

 all the soft parts readily separate, leaving the bones without any 

 of the ligaments or cartilages which are firmly fixed to them during 

 life. They are then put together by wires. &c., the cartilages being 

 represented by leather and cork. In this way it often happens 

 that the proportions are not exactly preserved, and, on reference 

 to an articulated skeleton in any museum, the inexperienced eye 

 may be greatly misled. Thus it is very common to represent the 

 thorax in the artificial skeleton as much shallower than it is in 

 nature, where its lower margin is on the average about midway 

 between the tup of the withers and the ground. Again, in the 



