62 
LECTURES ON HORSES. 
The lower end of the cannon-bone has two roller-like, smooth 
and polished surfaces, which play within correspondent concavities 
upon the summit of the pastern bone : the position of the latter, 
however, being obliquely forward, while the former stands in a 
perpendicular line, a large vacuity would necessarily be left be- 
hind, were not the sesamoid bones placed there for the purpose of 
completing the joint. These two little supplementary bones are 
kept in their places by ligaments, two running crosswise, attaching 
them to the pastern bone ; but their mainstay, that which princi- 
pally upholds them, and admits of the play or motion of them dur- 
ing the action of the fetlock-joint, is the suspensory ligament. The 
sesamoid bones are so bound to the supero -posterior part of the 
pastern, that the three together form a cylindroid dish-like hollow, 
into which is received the lower end of the cannon-bone ; and the 
weight from the latter preponderates upon one or other of the for- 
mer, depending upon the obliquity or line of direction the pastern 
takes on leaving the cannon in its course to the foot. When the 
pastern deviates but little from the perpendicular of the limb, it is said 
to be “ straight,” and is almost always made “ short ;” so that short 
and straight pasterns are consentaneous formations : the reverse, 
short and slanting pasterns, being incompatibles, or at least such a 
combination as is rarely seen, and is attended with disadvantages 
both of strength and action. When, on the other hand, the pas- 
tern forms, in leaving the cannon, a considerable angle, it is said 
to be “ oblique,” and is almost always extended in length, so as to 
assume the denomination of “ long” or “lengthy this is a dispo- 
sition of parts which also has its peculiar advantages, and one 
that would have its objects defeated or much abridged by any dis- 
proportionate shortening with the obliquity. 
In proportion as the pastern is upright in position, less weight is 
imposed upon the sesamoid bones, more upon the pastern bone, 
and vice versa. What pressure or weight the pastern-bone re- 
ceives descends to the coronet, and thence to the coffin-bone. But 
what becomes of the weight imposed upon the sesamoids, they 
having no bones below to transmit it to 1 They are in a somewhat 
similar situation to the splint-bones; they call upon their attaching 
bands — their ligaments — to support them under the load ; and 
their ligaments do so by yielding — they being elastic — so long as 
force is operating ; and the instant it is not, they, through elasticity, 
again recover their short lengths, and so raise the sesamoid bones 
into their places. This descent and ascent of the sesamoids is not 
to be compared with that imperceptible and disputed motion of the 
splint-bones ; on the contrary, it is a demonstrable and beautiful 
descending and ascending operation — a playing down and up, after 
the manner of a spring of most elastic and exquisite workmanship ; 
