( 242 ) 

 Physiology. — "About Odour-affinities" . By Prof. H. Zwaardemaker. 



(Communicated in the meeting of September 28, 1907). 



The great number of odours occurring in nature and in technics 

 may, by virtue of the current opinions in literature, be divided into 

 9 classes, which may be indicated by historical names 1 ), chiefly 

 borrowed from Linnaeus. These classes are : etherial odours, aromatic 

 odours, odores fragrantes, moschus odours, ally] odours, empyreu- 

 matic odours, capryl odours, narcotic odours, odores nauseosi. I 

 have selected from each class a representative which, chemically 

 well characterized, can in a very simple way be made fit for olfac- 

 tometric investigation (by dissolving the chemically pure odoriferous 

 material in paraffinum liquidum s ), with one exception, viz. muscon, 

 which is odourless in by itself odourless paraffine, and which there- 

 fore has been used mixed with myristine acid. They are: 



isoamylacetate 0.5°/ 



nitrobenzol 5% 



terpineol 2.5° < 



muscon 0.627% 



aethylbisulfide 1% 00 



guajacol 1% 



valerian acid lVooo 



pyridine 1°/, 



scatol l°/oo- 



If in the double olfactometer two of these materials are joined 

 together, there occur among the 36 combinations thus obtained no 

 real mixed odours, but because they are counterbalancing each 

 other, either an odourless mixture or rivalry is obtained. Odourlessness, 

 respectively indefiniteness of odour, with change into odourlessness 

 by rarefaction of I he airmixture, is met with, when the stimuli arc 

 weak; rivalry, i.e. the alternate preponderance of one or the other 

 of the two mixed odours is met with, when the stimuli are strong. 

 However, also in the last case the impression, made by the mixture, 

 is considerably weaker than the impression that every odour by itself 

 brings about. 



As unit of smelling-power I take the olfaction, i. e. the smallest 

 quantity of odour of a definite quality, which can be recognized 



') H. Zwaardemaker, Physiologie des Geruchs. Leipzig 1895 p. 207. 



2 ) Not water, but paraffinum liquidum has been chosen as a solvent because it 

 js desirable to work for months at a stretch with the same cylinders without 

 alteration ol the solution. 



