passage. As far as we know, all that takes place is that the incoming stimulus, the odorous molecule, is warmed and received by the nasal mucus.
Thus the very complexity of the structure both of the eye and of the ear helps us to comprehend their function.
But what can we deduce from a flat surface in which all we can see is a collection of cells with minute protoplasmic hairs projecting from their distal ends ? Obviously, little or nothing. We are, in fact, confounded by simplicity. It may be that we are here dealing with one of the essential properties of all living matter, little, if at all, altered from its primitive condition.
To the physiologist, then, olfaction is the most mysterious of all the senses. It still retains its secrets, and therein lies the fascination of its study.
Of late years, the exploration of this dark region of physiology has been, and is still being, vigorously pushed, and we shall now proceed to give what, however, can only be a brief and superficial account of the progress made and of the opinions held. Even so we shall be compelled to make an incursion into the high and dry realms of modern chemical and physical theory. That may not be good hearing, but what is still worse is that almost every single point we shall be discussing is a matter of controversy.
