LECTURES ON HORSES. 
9 
looking back and turning round with equal facility and rapidity, 
would all have been greatly impaired by a spine either directly 
straight or uniformly curved : in addition to which, none of the 
actions of the body, in particular gallopping and leaping, could 
possibly have been performed with the same efficiency they are at 
present. 
The arc of the spine forming the loins and croup is completed 
posteriorly by the tail, which, when of its natural length/ con- 
siderably extends it, both backwards and downwards. Then here 
is another part upon which weight may be imposed with great ad- 
vantage to the animal : the tail itself will assist in its maintenance, 
let alone its being placed immediately above the hind limbs or pos- 
terior columns of support; and the destruction of this arc, when 
the burthen is intended to be borne by it, forms, there cannot be a 
question, a decided objection to docking. Asses, we know, with 
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. 
I have already observed that the motions, although exceedingly 
limited between any two vertebrae, 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 resistible* 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. 
[To be continued.] 
b 
VOL. XV. 
