THE 
HE ufe of the bones is to give fhape and firmnefs to 
the body, to be levers for the nrufcles to aft upon, and 
to defend thofe parts from external injuries that are 
of greateft confequcnce to be preferved; as the brain, 
fpinal marrow, heart, gee. Their fibres .when firft 
formed are very foft, until by the addition of a matter, 
which is feparated from the blood into them, they grow by degrees to 
the hardnefs of a cartilage, and then perfeft bone: But this change is 
neither made in a very fliort time, nor begun in all the parts of the fame 
bone at once. Flat bones (Tab. i. and xxxi.) that have their fibres direfted 
to all fidcs, begin to offify in or near a middle point; but the cylindri¬ 
cal bones and all others, whofc fibres are nearly parallel, begin about the 
middle of each fibre; and thence Ihoot forth to their extremities; not 
always in continued lines, but frequently beginning new olfifications, 
which foon join the former. (Tab. i.) By the continual addition of this 
olfifying matter, the bones incrcafe till their hardnefs refills a farther cx- 
tenfion; and their hardnefs always increafing while they are grbwhw, the 
increafe of their growth becomes llowcr and flower, until they ceafe to 
grow at all; and in old perfons, (Tab- vi) and confumptive, (Tab. xxiii' 
