Notes on scientific research. 125 



The measurements performed with this apparatus gave the following results: — 



1. The minimum perceptibile is generally perceived quicker and with less smelling 

 material in cases in which the test-person is conscious as to what is going on 

 than vice versa. 



2. Test-persons observe scents which are known to them more readily and with 

 less waste of perfume than otherwise. 



3. Practice has great influence on the results. 



4. Central factors and experience have also a great influence on the results. 



5. During the first moments in which one begins to smell anything (the border- 

 land of sensation), the perception is still vague, i. e. it is undeterminable if the 

 scent in question appeals to the nasal organs or to those of taste or touch. 



6. In order to entirely perceive any odour and to be able to characterize it (border- 

 land of realization), both time and a further amount of perfume are required 

 beyond that necessary for mere perception. Well-known odours are more readily 

 perceived and also in lesser quantities than unknown ones. 



7. A state of excitement or a too vivid play of the imagination tend to prolong 

 the time required considerably. 



8. The excellence and keenness of the sense of smell is not influenced at all by 

 sexual differences. In comparing the two it was proved that experience was 

 the deciding factor. 



9. Children showed no difference in their detection of odours which they knew in 

 comparison to adults. However, they are more easy to lead astray by suggestion. 



10. The volume of the nasal space has no influence on the results. 



A table is then adduced in which it is shown by a great number of scents how 

 many millionths of a gram of scent per litre of air suffice in order to produce a 

 perceptible effect, which allows one to conclude how great the absolute quantity of 

 scent is contained in one respiration. As, however, only a fraction of the scented 

 particles reach the nasal mucous membrane, one can estimate that although barely 

 a single molecule of a strong perfume, for instance of musk, does not suffice to produce 

 a stimulus, a sharp nose^ however, can already detect the trillionth part of a gram. 

 Some perfumes are so strong that a single gram would be sufficient in order to pro- 

 duce a perceptible sensation to all the inhabitants of the earth (1600 millions). Hence 

 the nasal organs are a hundred-thousand times more sensitive than the methods of 

 spectral analysis. There is, therefore, no doubt that of all our senses that of smell 

 is the most sensitive. 



According to Henning's observations, the much discussed question if human beings 

 are capable of smelling liquid solutions of scents must be answered in a negative sense. 

 The sensations produced in such cases are not really those of smell, but rather tactile 

 ones, combined with those of taste and temperature. 



Experiments with aquatic animals prove that they are indeed capable of smelling 

 aromatic substances dissolved in water, but that their smelling sensations are mainly 

 affected by the non ionized scent particles which are diffused in water without being- 

 dissolved. The physiological process of smelling in human beings can be thus explained 

 that the molecules of perfume diffused in the air penetrate the mucous membrane and 

 are split up on the surface of the individual smelling cells. The intensity of the sensation 

 seems to depend on the greater or lesser number of scented molecules which act together. 



Opinions differ still widely as to the efficiency of the human sense of smell as well 

 as its meaning in biological, phylogenetical, physiological, psychological, and aesthetic 

 respect. 



