848 THE HORSE. 
into the knee and hock of the horseman without impropriety, and at the 
same time without any chance of a misunderstanding. 
THE TARSUS consists of six bones, disposed in two rows, the astragalus 
and os calcis forming the upper one, but the former bone alone entering 
into the tibio-tarsal, or hock joint, with the tibia. 
THE ASTRAGALUS (do7pdyados, a die) is an irregular bone, situated in 
front of the os calcis, between the tibia and the os scaphoides: it is 
divided into five surfaces: first, the supero-anterior surface, pulley-like 
and articulatory, corresponds with the inferior extremity of the tibia, and 
consists of two semicircular prominences, separated by a deep groove, 
taking a course obliquely outwards and forwards; secondly, the inferior 
presents a smooth convex surface with a roughened depression posteriorly, 
for ligamentous attachment, and articulates with the superior face of the 
os scaphoides; thirdly, the posterior is irregular, and presents on its 
surface four smooth faces for articulation with the os calcis, which are 
separated by roughened excavations. ‘The external side is marked by 
ligamentous impressions; the internal, smoother than the external, 
presents behind and below a little tubercle, which gives attachment to 
ligaments. 
Tre Os Catcts (the heel-bone).—This bone, forming the point of the 
hock, presents two surfaces, two borders, and two extremities; the ex- 
ternal surface is almost plain ; the internal is excavated as a groove; the 
anterior is slightly concave ; the posterior is straight and roughened ; on 
the superior extremity is a thick tuberous termination, to which the ham- 
strings are attached; its inferior extremity is large and concave, and 
presents four surfaces for articulation with the astragalus, os cuboides, 
and os scaphoides, and a median rough interspace to which ligaments 
are attached. 
THE Os CuBOIDES (xiBos, a cube) is situated on the postero-external 
sides of os cuneiforme magnum and os scaphoides, between the inferior 
extremity of the os calcis and the head of the external small metatarsal 
bone and also a portion of the superior extremity of the large metatarsal 
bone. It presents six surfaces: a superior, which articulates with the os 
calcis : an inferior by two facettes corresponds to similar ones situated on 
the large and external small metatarsal bones just mentioned ; internally 
two arthrodial surfaces occur, which face with similar surfaces on the os 
cuneiforme magnum and os scaphoides. ‘The external, anterior, and 
posterior surfaces are roughened for ligamentous attachment. 
Tue Os ScarHorbes is in figure triangular ; the superior surface smooth 
and slightly concave, is entirely articulatory, with the exception of a little 
groove, running to its middle from the outer side; this surface cor- 
responds with the under surface of the astragalus. The inferior surface 
is similar to the superior, except that it is shghtly convex, and articulates 
with the superior surface of the os cuneiforme magnum, and also on its 
internal angle with the os cuneiforme parvum; it offers also, on its 
postero-external face, two small diarthrodial surfaces for articulation with 
the os cuboides ; in the rest of its extent, it is roughened for ligamentous 
attachment. 
Tue Os CunerrormMe Macnum.—tThis bone, although smaller than the 
scaphoid, at the same time greatly resembles it; its superior surface 
articulates with the inferior surface of that bone; the inferior surface 
articulates with the large metatarsal bone ; its external border is provided 
with two arthrodial spots for articulation with corresponding ones on 
the os cuboides. The internal border also offers a spot which articulates 
