134 Wyman on the Cancelli of Bones. 
directly transmitted, and which in consequence of its curved 
form, is more likely to yield to compression than the convex 
surface on the opposite side to traction. 
The walls of the bone are still further supported by the 
disposition of the cancelli, which act as so many braces within. 
In addition 1o this, however, these last form a segment of an 
arch, and themselves support directly a portion of the weight 
of the body, and transmit it to the walls of the neck. If on 
the application of weight to the head of the bone, the neck 
yield at all, the effect will be tension of the fibres (bb) ; and 
in consequence of their resting beneath upon the fibres (aa) 
compression of these last. 
It is worthy of notice in connection with these directions 
of force, that the radiating series, (a a,) which support pressure 
by their rigidity, are the strongest, and the series at right 
angles and between them, which serve as braces, are more 
. slender; while in the curved series, (b 6,) which resist by their 
tenacity, are the strongest, and the braces which may be 
regarded as a continuation of the radiating series, are the 
weakest; precisely as would be the case in the frame of a 
building; the braces of the circular series become stronger as 
you approach the centre of the bone where the pressure 
becomes the greatest. 
The shell of the neck is of itself sufficient to support great 
weight, in virtue of its form and structure; but its power of 
resistance is still farther increased by the cancelli, which form 
within a light truss or framed arch; the long fibres at (a) 
transfer weight directly to the under side of the neck. They, 
as well as the shell of the neck at ( d,) are supported by the 
curved fibres (bb) and these in turn by the radiating fibres 
(a.) The whole may be regarded as equivalent to an increased 
thickness of those portions of the shell of bone above and 
below, which are the seats of the greatest strain and pressure.. 
The weight of the body is transmitted through the shaft of 
the femur to the condyles below, the space between these 
sustaining but little pressure. The lower portion of the thigh 
