hungriness, and the wish to satisfy it, or to get rid of it,
becomes imperative, and the dominant of consciousness.

Without doubt the sexual cravings are likewise so determined. Sex
libido is an expression of a certain concentration, a definite amount
peculiar to the individual, of the substance manufactured by the
interstitial cells, circulating in the blood. It arouses its effects
probably by (1) increasing the amount of reproductive material in
the sex glands in a direct chemically stimulating effect upon the
germinative cells, and so raising the internal pressure within them,
(2) stimulating the involuntary muscles within the walls and the
canals of the sex glands, and so, by augmenting the tenseness of the
muscles, elevating the total intravisceral pressure, (3) by a direct
chemical and indirect nervous effect upon the brain, the muscles, the
heart, as well as the other glands of internal secretion stimulating
the organism as a whole. Though the isolation in pure form of the
substance or substances involved has never been scientifically
achieved, their inference is entirely justified. It is indeed the only
comprehensible mechanism conceivable that will fit all the known facts
about the matter. And even though the assertions of Brown-Sequard were
only the exaggerations of a semi-charlatan, it is certain that some
day in the near future the particular substance, that he claimed he
had discovered, will be handed about in bottles for the inspection of
the curious.

Besides thyroxin, adrenalin, and the libido-producing secretion of the
interstitial cells, the substance produced by the paired glandlets,
situated behind the thyroid, the parathyroids, have a profound
influence upon the vegetative apparatus and the vegetative nervous
system. These direct the lime exchanges within the cells of the
organisms, including the nerve cells. It has been shown that lime is,
relatively, a sedative to cells. It raises the threshold or strength
of stimulus necessary to evoke a reaction. Removing the parathyroids
means removing the lime barrier, for with their deficiency there is a
change in, and then an escape, from the blood, of the lime, by way
of the kidneys. The result is sometimes an enormous increase in the
excitability of all the cells, and especially of the vegetative
apparatus. What that means for the individual whose comfort depends
upon a stability of the intravisceral tones and pressures may be
readily imagined.

The p