138 Wyman on the Cancelli of Bones. 
made by Mr. Lawrence many years ago, independently of 
its structure within, that “ex calce hominem” would be a 
safer rule, than “ea pede Herculem," gains additional force.’ 
In the above descriptions the minute structure of seve 
bones has been described as well as the nature of the force 
which they are intended to resist. It is not always safe to 
attempt to assign the final cause of animal structures, to indi- 
cate the intention of nature in certain conditions of things — 
though there can be no risk in describing in connection such 
conditions of organization as co-exist. As to the individual 
bones, it has been shown in what direction force or weight 
is applied to them, and in what direction the cancelli are 
arranged within them. On the lumbar vertebre there is ver- 
tical pressure; within, the principal fibres are also vertical. 
On the neck of the thigh bone the weight of the body is 
applied obliquely to the end of an arm; within it there is a 
combination of fibres, giving strength with lightness, which 
forms a frame mechanically adapted for resisting the weight 
which rests upon it. On the astragalus the pressure again is 
vertical, but this bone rests on two others, one below it, the 
os calcis, and the other in front, the scaphoides; within there 
exists two series of cancelli directing the pressure on the sur- 
faces of support, and very nearly the same description applies 
to the os calcis. A certain direction of fibres in all these 
instances co-exists with a certain direction, or certain direc- 
tions, of the transmission of pressure. From this constant 
association of structure and function, the ied «n 
unavoidable, that they are means and ends. - © 
The next subject for consideration i is, as to the pi pun 
some more general condition to^ which these” individual 
instances are subservient — and. this involves the necessity 
of inquiring, to what extent similar’ structures ‘exist Jin other 
members of the’ Mammiferous series? After having - made 
numerous sections of the. corresponding: bones of other! ani- 
mals, searcely any indications of ‘these peculiar ai 
! Lectures on Physiology, Zoölogy and the Nat. Hist. ‘of Mar, p. 124. Yona isi 
