114 THE CANCELLI OF BONES 



III. THIGH 



The lower portion of the thigh has only a thin 

 shell, but here its diameter is largest and filled 

 with the cancellated structure, which especially in 

 the lateral portions has a very definite arrange- 

 ment ; the cancelli forming a series of pillars, 

 which ascend very nearly vertically from the sur- 

 faces of the condyle to the walls of the bone 

 above them, which are bent inwards as the bone 

 diminishes its diameter towards the middle of the 

 shaft. A corresponding arrangement exists in 

 the two extremities of the tibia, where the surface 

 which is the seat of pressure is sustained by col- 

 umns of bony fibres extending to the walls above 

 or below it, according as the upper or lower por- 

 tion of the bone is examined. This structure has 

 been distinctly figured and described by Bour- 

 gery and Jacob. 1 The cancelli are, as in the parts 

 before described, prevented from lateral flexion 

 by braces which are interposed at right angles to 

 their direction. 



IV. ASTRAGALUS 



The tibia alone bearing vertically on the astrag- 

 alus, this last bone will necessarily sustain in 

 each foot one half the weight of the body, or the 

 whole of it when it is supported on one foot. 



1 Op. cit., Tome I. pp. 119 and 121, also PI. 43, Figs. 3, 4, and 7. 



