THE BONY TRUNK. 75 



in the first twelve is considerable, for the purpose of giving 

 a long lever to the shoulder muscles. It is these processes 

 that give height to the withers ; and as they are covered 

 with muscles that act powerfully, so their length is 

 of great consequence to progi'ession. Their four oblique 

 processes are small, as well as their transverse. They arti- 

 culate with each other by their anterior and posterior sur- 

 faces, and by their oblique processes : each also articulates 

 with two ribs, one upon either side. As they advance they 

 increase in size, and are pierced by the spinal canal equally 

 enlarged. Between each is interposed a substance of the 

 mixed nature of cartilage and ligament, which is most com- 

 pressible at its sides, permitting the motion of the spine, 

 and forming, by the solidity of its centre, a fulcrum, or pivot, 

 for the bones to move on. This interposed substance loses 

 its elasticity in the old horse, and becomes nearly converted 

 into bone ; to which we may attribute that stiffness in old 

 horses when attempting to rise after lying down ; and the 

 want of that springy gait which is felt when upon the back of 

 the young horse. 



The bones of the loins, or lumbar vertebras (Skel. 4, 4, 4, 

 4, 4, 4), have somewhat larger bodies than the bones of the 

 back, and broader spinous processes. Their transverse pro- 

 cesses bear no comparison to those of any other vertebrae ; 

 being extended out to supply the place of the ribs, and to 

 afford attachment to the muscles of the back : the last 

 unites with the sacrum (Skel. 5, 5, 5, 5, 5). 



With the loins, the true vertebrae end ; and here it may 

 be as well to speak of the peculiarities appertaining to them. 

 The head and first bone of the neck have very free motion, 

 principally upwards and downwards, as when the horse 

 tosses his head. The joint formed by the next bone of the 

 neck with the first has likewise a very easy movement, but 

 it is chiefly towards either side, or rotatory, as when the 

 animal shakes his head or looks round about it. The re- 

 maining neck bones move very freely altogether, though 

 but slightly upon one another ; they come into play whenever 

 the horse turns his head to one side or to the other, as 

 likewise when he raises the head upward, or bends it 

 downward. 



The bones of the back have the least motion of all ; their 



