1256 THE SENSE OF SMELL. 



In both sight and hearing we have this interesting fact, namely, that 

 vibrations, which are either enormously rapid or comparatively slow, are in both 

 cases incapable of acting as stimuli. We have, according to Ramsay, an analogy 

 in the case of smell, for bodies of low molecular weight, and having therefore 

 a high vibrational period are odourless. In the case of smell there are no 

 known bodies of slow vibrational periods incapable of producing a sensation ; 

 but in the case of taste there are indications that there exist both a lower as 

 well as an upper margin to our sensation. 



The physical condition of the stimulant. — E. H. Weber 1 main- 

 tained that if you allow a 10 per cent, watery solution of eau de Cologne 

 to flow into the nose, it fails to produce an effect upon the sense of smell ; 

 and he concluded that if we are to smell them, odorous particles must be 

 carried by the air into the cavities of the nose. Eecently Aronsohn 2 found, 

 on repeating these experiments, that such solution is highly irritating 

 to the mucous membrane of the nose, and produces partial anosmia. It 

 is supposed that the olfactory cells swell up, become waterlogged, and 

 are no longer sensitive to stimuli, and on account of this action Aronsohn 

 explains Weber's inability to smell the watery solution of the eau de 

 Cologne. In other experiments Aronsohn replaced the water by normal 

 saline, and states that under these conditions the scent produces its 

 normal effect. In all these experiments we must bear in mind that the 

 true olfactory region of the nose is now known to be situated in quite 

 the upper part of what is really nothing more than a narrow chink. It 

 is therefore a matter of very considerable difficulty to displace the 

 air from this chink and replace it with the scent in a fluid form. But 

 with this successfully accomplished, I myself, and three other persons 

 upon whom I have experimented, have been unable to perceive any odour 

 at all in the case of 5 or 10 per cent, solutions of eau de Cologne. The 

 experiment may best be performed as follows : — The person to be experi- 

 mented upon lies upon his back on a bench with his head hanging 

 downwards over the end, so that the olfactory region of the nose is 

 lowest. Two glass funnels are connected by tubing with a T-junction, 

 and from the third limb of the T, another tube passes into one nostril. 

 Warm normal saline is allowed to flow from one funnel until both nasal 

 cavities are filled, and the air-free solution falls upon the ground. This 

 is then displaced by warm scented normal saline. 



The following experiment indicates that although the nose is filled 

 with odorous particles, yet they are incapable of affecting the olfactory 

 nerves, and only do so when the air containing them is set in motion. 

 The subject of this experiment performs several acts of respiration in 

 rapid succession, so as to render himself apnoeic. Under these con- 

 ditions he is then able to remain perfectly immovable, without 

 breathing, for from one to three minutes. A bottle containing ammonia 

 is unstoppered under his nose ; the vapour diffuses into the nose, is 

 irritative, but cannot be smelt. If, after waiting say tw T o minutes, 

 he then pinches his nose so as to imprison the ammonia vapour already 

 within it, walks into the fresh air, removes his fingers from the nose, 

 and inspires through it, the ammonia is at once smelt. These ex- 

 periments may be repeated with eau de Cologne, camphor, bergamot, 

 etc., and indicate that odorous particles do not stimulate the end- 



1 Arch. f. Anat., Physiol, u. wissensch. Med., 1847, S. 342. 



2 " Exper. Untersuch. z. Physiol, des Geruches," Inaug. Diss. 



