343 THE SKELETON IX GENERAL 



OF THE SKELETON IN GENERAL 



TiiK NAMt; ski:li:iu\ hus Lcl'Ii gi\ tu fruin the Greek wurd o-kcAAu) (to dri/), 

 it being the only part of the body which will bear desiccation without 

 change of form. In the vcrtehrata it is an internal bony framework, but in 

 the Crustacea it invests tlic soft parts, and forms an insensible covering to 

 them, while at the same time it serves the purpose of locomotion. In both 

 these divisions of the animal kingdom 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 tlie 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; 2nd, where, by 

 means of the ribs and sternum, it constitutes the thorax and its appendages, 

 the anterior extremities ; and, 3rdly, where, in tlie shape of the pelvic arch, 

 it protects the organs of generation, and, through the posterior extremities 

 prolonged from it, assists in locomotion. The superior of these arches, from 

 containing the brain, and its prolongation, the spinal cord, is called the 

 neural arch. The inferior is termed the luvmal arch {oXfia, blood), because it 

 protects the lieart 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 ha>mal arch is nearly as complete, these animals having cervical 

 ribs ; while the dugongand 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 boxks of the Horse, as of theullier 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, etc., 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 articu- 

 lated skeleton in any nmseum, the inexperienced eye ma}- 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 top of the withers and the ground. Again, 



