THE SPINE. 11 



great apparent facility, and comparative ease, carry their loads upon 

 their croups : docking, one would think, must tend to render this 

 carriage difficult. 



The vertebra, or bones composing the spine, are exceedingly ir- 

 regular in their figure, and remarkable principally on account of 

 protuberances and projections growing from their sides and supe- 

 rior parts. The superior projections are conspicuous for their length, 

 particularly those forming the withers. In fact, it is the length of 

 these processes that regulates the height and fineness of the withers. 

 Altogether,, the protuberances and projections may be regarded 

 as constituting a series of levers for the attachment of muscles, 

 many in number and great in power, on which mainly depends 

 the strength in action of the animal, as well as his capability as a 

 beast of burthen. 



T have already observed that the motions, although exceedingly 

 limited between any two vertebrse, are pretty extensive in the 

 entire spine, owing to the number of its component pieces. The 

 spine was required to be a very strong and resistant structure ; at 

 the same time it was required to have the power of flexure and 

 curvation, in order to accommodate itself to the various positions and 

 movements of the body during progression ; all which could not have 

 been effected in the same piece of mechanism without a manifold 

 division of its component parts. Whenever the motion between 

 two bones is of an extensive or varied character, the liability to 

 dislocation or displacement between them becomes great: the 

 more completely the bones are locked or dove-tailed together, the 

 more limited becomes the motion between them, but the more 

 secure they are against liability to dislocation. Such is the admi~ 

 rable mechanism of the spine, that both these desiderata are insured. 



