LECTURES ON HORSES. 
7 
gether — comprehending its?entiredine---having something the figure 
of a double jf turned lengthwise and united. 
An artist would say, “ Why this is precisely the superior outline 
of a horse.” We must regard it as the key-stone of the edifice — 
the great bond of union of the two sides or halves into one whole. 
It is the most important part of the structure. It is composed of 
no less than thirty pieces, called vertebra : — seven in the neck, 
eighteen in the back, five in the loins, with the addition of the 
croup and the tail ; and these united one to another, by an elas- 
tic gristly substance, to the interposition of which is ascrib- 
able that pliancy and flexibility which the spine — for so this chain 
of bones is called — in the living animal is known pre-eminently 
to possess. The sinking down of the back under the imposition 
of weight at the time that the rider mounts — the spring} 7 and easy 
seat the rider finds in the hollow or middle of the back, and the self- 
adjusting power of the spine to the various inflexions of the body, 
are all attributable to this property of elasticity which the vertebral 
chain derives from its thirty gristly inter-layers. Supposing it bad 
been from beginning to end one undivided piece of bone, what would 
have been the consequence 1 Why that the animal could have 
possessed no flexibility either in his neck, back, loins, or tail, and 
must, therefore, have moved about upon his legs, stiff in all these 
parts, as though he were affected with tetanus or locked-jaw. As 
it is, there exists a little yielding, a very little, between every two 
vertebra?; but this, multiplied by the number of the vertebrae, 
gives, as an aggregate, to the entire spine a very considerable ex- 
tent of flexibility. There is, perhaps, no occasion on which this 
flexibility of the spine is better seen than at the time a horse is 
twisting his head round to bite himself, or scratch his cheek with 
his hind leg, unless it be in the remarkable bending evinced by 
an ass at the time he crawls under a low rail. 
The figure the spine describes in its course is that, imperfectly, 
of a double S, or of two ff of unusual lengths, placed horizontally, 
and united thus . There appear two arcs formed by 
it, one at the upper part of the neck, another commencing in the 
back, behind the blade-bone, and running through the loins and 
croup to the tail. These, therefore, we may take to be the most 
