102 THE CANCELLI OF BONES 



point of view they may be regarded in nearly all 

 these bones as a series of " studs " and " braces." 



2. The direction of these fibres in some of the 

 bones of the human skeleton is characteristic, 

 and, it is believed, has a definite relation to the 

 erect position which is naturally assumed by man 

 alone. 



These structures are the most conspicuous in 

 the lumbar portion of the vertebral column, in 

 the thighbone, both in its neck and lower ex- 

 tremity, in the tibia, in the astragalus, and the os 

 calcis. It should be remarked, however, in ad- 

 vance, that they are not equally distinct in the 

 bones of all individuals, nor at all periods of life. 

 The cancelli of the bones of young subjects gen- 

 erally have between them rounded areobe, and do 

 not appear to assume one direction more than 

 another. In very old subjects they seem to be 

 less clearly defined than in adult and middle-aged 

 skeletons. In these last, while considerable va- 

 riety exists, I have rarely failed to recognize the 

 general plan of the arrangement of the cancelli. 

 In bones filled with fat the structure is obscured, 

 but it is readily exposed by washing them in a 

 solution of potash or other alkali. 



I. VERTEBRA 



The functions of the vertebrae are threefold : 

 they serve as columns for the support of 



