ethereal undulations emanate from a source at a distance (it may be like starlight at an enormous distance) from the sensory end-organ, whereas in the case of odour the undulation is supposed to be generated by the odorous molecule in close proximity to the end-organ.
The theory makes no attempt to explain how the olfactory hairs respond to these hypothetical ethereal waves.
Finally, we have the question of the olfactory pigment to consider, and in this matter we cannot do better than follow the exposition of William Ogle, an English physician who wrote as long ago as 1870, As will be seen, he forestalls the modern undulatory theory of olfaction in a remarkable manner.
Ogle contends that the presence of pigment must be of great importance in the function for the following reasons :
First, the epithelium of the olfactory region is pigmented, while that of the rest of the nasal chamber and sinuses is devoid of colouring matter.
Secondly, there seems to be some correspondence between the degree of pigmentation and the acuteness of smell, as the following facts suggest :—
In macrosmatic animals, such as the dog, cat, fox, sheep, and rabbit, pigmentation extends over a larger space and is darker in tint than in man.
