198 Wyman on the Cancelli of Bones. 
ing from the upper to the lower face of the vertebra, receive 
the weight which they sustain on their ends; and this they 
will sustain in virtue of their rigidity. If they have a tendency 
to yield, it is either by being crushed, or by bending in 8 
lateral direction. This last is prevented by the transverse 
cancelli which are placed at right angles to the vertical ones, 
and serve the purpose of “braces.” The cancelli of the 
lumbar vertebrz are, therefore, arranged in conformity with 
the demand for resistance. "The arrangement in question 1s 
rarely obvious above the last dorsal vertebra ; it is, however, 
present in precisely that part of the column where the pressure; 
and, consequently, the demand for resistance is greatest. - 
I. NECK OF THE THIGH BONE. 
The whole weight of the head, trunk, arms, and pelvis, 
rests on the heads of the two thigh bones, or, more or less 
on one of them, according to the attitude of the body when 
in a state of rest. When the body is in motion they will 
sustain, in addition to this, the momentum of the trunk as it 
descends upon them in walking, running, jumping, &c. The 
heads of the bones are themselves immediately supported by 
the neck, the axis of which forms an angle of about 120° 
with that of the shaft of the’ bone, if the lower angle be 
