There are people who suffer from asthma when they go near horses. To enter a stable or to sit behind a horse is to them a certain means of bringing on an attack.
This susceptibility and the peculiar form taken by the reaction remind us of hay fever. In sufferers from this troublesome complaint the pollen of certain plants has an irritating effect upon the mucous surfaces of the eyes, nose, and bronchial tubes. So in like manner recent investigation has shown that there is in the blood of the horse a proteid substance which acts as an irritant poison to those susceptible people. Their asthma, therefore, is merely a manifestation of the irritation produced by the poisonous body or its emanation when it is borne to them through the air. Similarly we are justified in arguing that cats 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.[[2]] And the simultaneous irritation of the eyelids, and in the case of the pollen and horse effluvia the bronchial tubes, shows that these resemble in their action the simple chemical irritants, and not the odours.
[2]. 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.
It must be remembered, however, that, as we have said, the cat and the spider effluvia induce an emotional effect simply, without local irritation. And emotional change not only follows, it may also precede, the perception of an odour.
The following anecdote of Goethe, for example, shows how smell may affect the personality before it is recognised as an odour by the consciousness:
“An air that was beneficial to Schiller acted on me like poison,” Goethe said to Eckermann. “I called on him one day, and as I did not find him at home, I seated myself at his writing-table to note down various matters. I had not been seated long before I felt a strange indisposition steal over me, which gradually increased, until at last I nearly fainted. At first I did not know to what cause I should ascribe this wretched, and to me unusual, state, until I discovered that a dreadful odour issued from a drawer near me. When I opened it I found, to my astonishment, that it was full of rotten apples. I immediately went to the window, and inhaled the fresh air, by which I was instantly restored. Meanwhile his wife came in, and told me that the drawer was always filled with rotten apples, because the scent was beneficial to Schiller, and he could not live without it.”
I wish to emphasise, for the sake of my argument, that Goethe underwent a profound constitutional disturbance, with its attendant discomfort, before he realised that its cause was an odour.