106 THE CANCELLI OF BONES 



the largest, a section at right angles to its axis 

 being oval, and the long diameter perpendicular. 



2. In increasing the thickness of the wall of 

 bone on the under side of the neck and adjoining 

 portion of the shaft, on to which a large portion 

 of the weight of the body is directly transmitted. 



3. In having the cancelli of each femur so 

 arranged as to form a segment of a framed arch 

 or truss, which cooperates with the external shell 

 in sustaining the weight of the body ; the necks 

 of the two femora forming together opposite seg- 

 ments of an arch. 



The first and second of these conditions has 

 been frequently adverted to by anatomical writ- 

 ers, but the third has almost invariably escaped 

 observation. 



Sir Charles Bell, whose views of the animal 

 mechanism are generally so beautiful and true, 

 has not manifested his usual accuracy in his de- 

 scription of the structure of the neck of the thigh, 

 as given in his tract on Animal Mechanics. One 

 who examines this bone, he says, " will find that 

 the head of the thigh stands obliquely off from 

 the shaft, and that the whole weight bears upon 

 what is termed the inner trochanter ; and to that 

 point, as to a buttress, all those delicate fibres 

 converge, or point from the neck and head of the 

 bone." A careful examination of a section of 



1 Op. cit, p. 14. 



