medium, the essential condition of
the change of matter, of the production of the heat and of the
force by which the temperature of the body is kept up, and the
motions of the blood and all the juices are determined, so has gold
become the medium of all activity in the life of the state."

And blood-corpuscles being like coin in their functions, and in the fact
that they are not consumed in nutrition, he further points out that the
number of them which in a considerable interval flows through the great
centres, is enormous when compared with their absolute number; just as
the quantity of money which annually passes through the great mercantile
centres, is enormous when compared with the quantity of money in the
kingdom. Nor is this all. Liebig has omitted the significant
circumstance that only at a certain stage of organization does this
element of the circulation make its appearance. Throughout extensive
divisions of the lower animals, the blood contains no corpuscles; and in
societies of low civilization, there is no money.

Thus far we have considered the analogy between the blood in a living
body and the consumable and circulating commodities in the body-politic.
Let us now compare the appliances by which they are respectively
distributed. We shall find in the developments of these appliances
parallelisms not less remarkable than those above set forth. Already we
have shown that, as classes, wholesale and retail distributors discharge
in a society the office which the vascular system discharges in an
individual creature; that they come into existence later than the other
two great classes, as the vascular layer appears later than the mucous
and serous layers; and that they occupy a like intermediate position.
Here, however, it remains to be pointed out that a complete conception
of the circulating system in a society, includes not only the active
human agents who propel the currents of commodities, and regulate their
distribution, but includes, also, the channels of communication. It is
the formation and arrangement of these to which we now direct attention.

Going back once more to those lower animals in which there is found
nothing but a partial diffusion, not of blood, but only of crude
nutritive fluids, it is to be remarked that the channels through which
the diffusion takes place, are mere excavations through the
half-organized substance of the body: they have no lining membranes, but
are