ear as well as in the eye, and its presence in these organs seems to be essential to their activity.
It is to be noted that the pigment does not occur on the nerve structure in any of those end-organs, but external, though contiguous to it. In the eye, it lies in contact with the rods and cones of the retina ; in the nose, with the olfactory hairs ; in the ear, with the terminal bodies of the auditory nerve.
Hence the pigment, he supposes, must be associated with the reception of the sensory impressions.
In the eye and the ear those impressions are undulatory in character. That being so, he holds that the undulatory theory of olfaction also is probably the correct one.
Ogle finishes with the remark that the theory would be strengthened if it could be shown that pigment was specially suited for the absorption and modification of undulations.
It is interesting to us to learn that claims are now being made that pigment does possess the power necessitated by Ogle’s theory. Atall events, there is a theory of vision (Castelli’s) which claims for the ocular pigment the power of absorbing and modifying light waves, and Heyninx holds that the olfactory pigment possesses a similar property.
Summing the whole matter up, then, we may
