Why then, you may ask, if such unity exists, why this dissimilarity in
the tissues of the respective bodily organs? How is it that a bone in
its stonelike hardness is essentially the same as the infinitely tender
tissues of the eye? This difference is due to and accounted for by the
adaptation of certain portions of the immense accumulation of cells to
diverse functions, which has necessitated the variable conformity of the
supporting elements. But all of these elements are in the blood, which
carries them in the necessary quantities to the different organs to
which they belong and where they are utilized to replace used-up matter.