That, on the other hand, those odorous substances are by no means inactive bodies, may be inferred from their great volatility, known as it is in physical science that volatility is owing to a state of atomic activity.  Prevost has described two phenomena that are presented by odorous substances.  One is that, when placed on water, they begin to move; and the other is, that a thin layer of water, extended on a perfectly clean glass plate, retracts when such an odorous substance as camphor is placed upon it.  Monsieur Ligeois has further shown that the particles of an odorous body, placed on water, undergo a rapid division, and that the movements of camphor, or of benzoic acid, are inhibited, or altogether arrested, if an odorous substance be brought into contact with the water in which they are moving.

Seeing, then, that odorous substances, when coming in contact with liquid bodies, assume a peculiar motion, and impart at the same time motion to the liquid body, we may fairly conclude that the specific formative capacity of the protoplasm is owing, not to the protoplasm itself, since it is everywhere alike, but to the inherent, specific, odoriferous substances.

I shall only add that Professor Yaeger’s theory may be carried farther yet.  Each metal has also a certain taste and odour peculiar to itself; in other words, they are also endowed with odoriferous substances.  And this may help us to explain the fact that each metal, when crystallizing out of a liquid solution, invariably assumes a distinct geometrical form, by which it may be distinguished from any other.  Common salt, for instance, invariably crystallizes in cubes, alum in octohedra, and so on.

Professor Yaeger’s theory explains further to us that other great mystery of Nature—­the transmission from parent to offspring of the morphological speciality.  This is another puzzle of the biologist.  What is there in the embryonal germ that evolves out of the materials stored up therein a frame similar to the parents?  In other words, what is there that presides over the preservation of the species, working out the miniature duplicate of the parents’ configuration and character?  It is the protoplasm, no doubt; and the female ovum contains protoplasm in abundance.  But neither the physicist nor the chemist can detect any difference between the primordial germ, say of the fowl, and that of a female of the human race.

In answer to this question—­a question before which science stands perplexed—­we need only remember what has been said before about the protoplasmic scent.  We have spoken before of the specific scent of the animal as a whole.  We know, however, that every organ and tissue in a given animal has again its peculiar scent and taste.  The scent and taste of the liver, spleen, brain, &c., are quite different in the same animal.

And if our theory is correct, then it could not be otherwise.  Each of these organs is differently constructed, and as variety of organic structure is supposed to be dependent upon variety of scent, there must necessarily be a specific cerebral scent, a specific splenetic scent, a specific hepatic scent, &c. &c.  What we call, then, the specific scent of the living animal must, therefore, be considered as the aggregate of all the different scents of its organs.