and spiders may throw off an effluvium which is irritating to those susceptible to it.
But it is to be noted that the antipathy in these last instances manifests itself, not in a tissue change, but in a feeling of the mind, an emotion. Nay more, these people do not smell the cat or the spider, except in the way that James I. “smelled” gunpowder. Nevertheless, the irritant must travel through the air as an odour does, and it probably enters the organism by the mucous membrane of the nose.
But does it act upon the olfactory cells ? Here we encounter, I must confess, a serious obstacle to an acceptance of this theory.
The interior of the nose is sensitive not only to odours, but also to certain chemical irritants. Any one who has peeled a raw onion or has taken a good sniff at a bottle of strong smelling-salts knows what I mean. Now, the chemical irritant, in the latter case ammonia gas, affects not the olfactory nerve, but certain naked nerve fibrils in
the mucous membrane belonging to what is known as the fifth cranial nerve, a nerve of simple sensation.[1] And the simultaneous irritation of the eyelids, and in the case of the pollen and horse effluvia the bronchial tubes, shows that these
- ↑ The difference between those two sensations becomes clearly evident when an anosmic person is peeling an onion. The usual irritation of the eyes and nose is felt and manifested, but the patient is unaware of any odour.
