ANATOMY OF THE HORSE. O 
Difference —The external is commonly rather larger than the 
internal bone; they are, however, with more certainty distin¬ 
guished by their articulatory surfaces. 
Connexion —The external bone supports the unciform ; the in¬ 
ternal, the trapezoid : both are attached to the large metacarpal 
bone. 
Development —In the growing animal the splint bones are 
maintained by cartilago-ligamentous connexions: in most adult, 
and in all old subjects, the ligamentous substance becomes con¬ 
verted into osseous matter. 
I . , - , . 1h *' ir i 
OF THE PASTERN. 
The pastern, corresponding to the first phalanx of the human 
foot, is supported by the pastern bone; but it has also two ap¬ 
pendices, the sesamoid bones, which are necessary to the forma¬ 
tion of the fetlock-joint. 
PASTERN BONE. (OS SUFFRAGINIS.) 
Situation —Below the cannon bone, with which, from taking 
an oblique direction , it forms an obtuse angle. 
Form —Cylindroid, flattened before and behind ; larger supe¬ 
riorly than interiorly: about one-third the length ol the cannon 
bone. 
Division —Into body, and superior and inferior extremities. 
The body presents two surfaces. The anterior is even and 
convex : the posterior is uneven, but flattened, and displays a 
slightly depressed triangular portion, into the asperous angle ol 
which is implanted the short sesamoid ligament. 
The superior or larger extremity consists of two shallow ar¬ 
ticular cups, laterally, with a deeper transverse articular groove 
running between them, in which lay the condyles and middle 
eminence of the lower extremity of the cannon bone. Behind, at 
the sides of the cups, are two tuberosities, to which are fixed the 
crucial ligaments. 
The inferior extremity is bi-convex or condyloid; consisting of 
two equal, articular, semi-cylindroid convexities, parted by a 
transverse shallow depression, running from before backward, but 
more completely separated by a little pit behind. The asperous 
prominences on the sides are for ligamentous attachment. 
Connexion —With the cannon and small pastern bones, and 
with the two sesamoids. 
SESAMOID BONES. (OSSA SESAMOIDEA.) 
Number —Two.— Situated at the back of the articulation formed 
by the large pastern and cannon bones. 
