135 Wyiman on the Cancelli of Bones. 
On making a longitudinal section of this bone (Fig. 4.) two 
series of cancelli are distinguishable at sight — one, a nearly ver- 
tical series (a, ) one end of which sustains the arched portion 
of the astragalus on which the tibia bears, and the other rests 
on the surface beneath, which articulatés with the os calcis ; 
the second ( b, ) a horizontal series nearly at right angles to the 
preceding, one end of which rests on the vertical series and 
the other on the surface articulating with the scaphoid bone. 
In the angle formed by these two series is a third (c,) much 
less regular, the direction of which is not well defined, but 
has a general tendency downwards and forwards towards the 
anterior and inferior articulating surfaces of the bone. ‘This 
portion sustains no direct pressure. 
V. OS CALCIS. 
It is through this bone that the weight is at last transmitted 
to the ground, and this takes place in two different directions ; 
one directly through the tuberosity of the heel, and the other 
indirectly through that surface which articulates with the 
cuboid bone, and this in turn with the 4th and 5th toes. The 
os calcis, however, does not simply form a basis of support; it 
is at the same time one of the arms of a lever by which the 
body is raised from the ground under the influence of great 
muscular action. The whole foot forms an arch, one end of 
which springs from the ground in the os calcis, and the other 
from “the ball of the foot” or the ends of the metatarsal 
