Wyman on the Cancelli of Bones. 197 
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 thigh bone, both in its 
neck and lower extremity, in the tibia, in the astragalus and 
the os calcis. It should be remarked, however, in advance, 
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, generally have between them rounded areolz, 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 consid- 
erable variety 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 itis readily exposed 
by washing them in a solution of potash or other alkali. 
I. VERTEBRA. 
The functions of the vertebre are threefold ; — they serve 
as columns for the support of weight; they form, by their 
union, a canal for the lodgment and protection of the spinal 
marrow ; and constitute a series of levers for the application 
of muscular force. The first of these functions is performed 
by the * body," whose special use in a given region is to sup- 
port the weight of the head, arms, and of all that portion of 
the trunk which is above it; which weight acquires its 
maximum in the lumbar region, where the vertebrae acquire 
their greatest size. The pressure on all the vertebre is 
. If a section be made through a lumbar vertebra, the 
areolz between the cancelli will be found to have generally 
à quadrangular form, and the direction of the cancelli either 
vertical or transverse. (Fig. 1.) The vertical ones extend- 
> This and the foll menu intended merely as plans of the cancelli, the 
akeh SA opp th bræ, For courte figures of ihe bones 
S aterd neck o e e verte and astragalus, see the pla 
