PHYSIOLOGY OF OLFACTION 81 



olfactory organs are said to call forth no sensations of 

 smell, and Valentin's statement that mechanical stimuli 

 will produce unpleasant olfactory sensations has not been 

 confirmed. Aronsohn (1884b), after filling the nasal 

 cavity with warm physiological salt solution led a direct 

 electric current through this cavity with the result that 

 certain obscure sensations were produced depending upon 

 whether the anode or the cathode was within the nose. 

 With the anode in the nose a sensation was called forth 

 on opening the circuit; with the cathode in the nose on 

 closing it. There was, however, no evidence to show 

 that these effects were not due to a stimuation of tri- 

 geminal endings instead of olfactory endings. Althaus 

 in 1869 recorded as the outcome of electrical stimulation 

 a phosphorous-like smell in a patient suffering from 

 double trigeminal paralysis. Apparently the electric 

 current is a true inadequate stimulus for the olfactory 

 organ, but its peculiarities are very incompletely under- 

 stood. Aside from this and the effects from solutions 

 as described by Veress, inadequate olfactory stimulation 

 seems not to exist. 



The adequate olfactory stimulus for both water-in- 

 habiting and air-inhabiting vertebrates is a solution in 

 contact with the olfactory hairs and perhaps formed in 

 part within these bodies. The solvent is probably first 

 the olfactory mucous which receives the solute from the 

 current of water or of air that passes over its outer sur- 

 face. This watery solvent, which from its nature must be 

 almost universal in its dissolving power, passes the solute 

 on to the olfactory hairs whose capacity as receptors is 

 probably limited by their lipoid composition. Only those 

 substances that are soluble in lipoids can be taken up by 



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