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 pancreas likewise acts as a sedative to the vegetative apparatus.  In particular, this applies to the sugar mechanism in the liver under the discipline of the check and drive organization.  The adrenal and the pancreas are the direct antagonists in the struggle for control of sugar.  Removal of the adrenals will cause a decrease in the amount of sugar in the blood, while removal of the pancreas will produce an increase.  Excess of sugar in the blood may thus be concomitant with changes of character considered incorrigible.