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* é ‘The constitution of the perfume is the most important thing for the kind of smell. 
aoe the reaction of the osmophoric group with various osmoceptors only the finer 
- dulling of the smell is caused, as a rule. There is hardly a chemical characteristic 
existing, whose influence on -the sense of smell is always approximately the same. 
In symmetrical trinitrotoluene the smell of musk first appears, when an additional 
alkyl is joined on to the molecule. Likewise with the ionone perfumes two methyl 
_ groups at least are necessary for producing the smell of violets, which only becomes 
distinctly noticeable when three methyl groups are added. Phthalide also is odourless, 
and only with isobutyl-phthalide is the celery odour Obtained. In this connection 
however, perfumes. are also known (vanillin and coumarin) which are built similarly 
- ~ tothe above, in which however, the entrance of alkyl groups is of no Seni C cues, 
or even damaging for the odour. 
A universal rule on the relations between smell and constitution of chemical 
compounds cannot on this account be further set down, since the influences of the 
4 central nervous system on the results of investigation, and the reactions taking place 
| 2 within the human body, give various» individual results. Only uncertain information 
can be indirectly obtained as regards the question, “with which compound in the 
organism do the effective odoriferous substances react?” since it is a case of unweighable 
quantities with perfumes. 
In connection with this work of Ruzicka, relerence may be made to the remarks, © 
which the theory of Teudt') on the origin of smell, has caused many authors”) to make. 
~ Amongst other things T. H. Durrans observes that Teudt does not appear to know the 
works of the physiologists Zwaardemaker and Backman’). Further it is not proved 
that the molecules Of the perfume would be altered in no way through the streaming 
ont of the odour. Facts like the fatigue phenomena and Kremer’s*) experiments on 
_ the absorption of perfumes in lipoid-containing water spoke against the assumption 
of Teudt. Teudt’s theory also cannot be brought into dereement with the law of the 
conservation of energy. | 
ain. a similar manner Parry raises several objections against these phantastic 
speculations, and emphasises that the smell of a body is a property which also 
depends on the person who smells, and cannot be treated as an objective phenomenon. 
Smell and Chemical Constitution.—Referring to an earlier work on Smell and 
Chemical Constitution®), T. H. Durrans®), in a controversy with E. J. Parry, emphasises 
_ that between the smell and volatility of a substance there exists no fundamental 
connection. According to Zwaardemakers proofs’), odour strength is independent of 
the ee ee phase, but depends on the solubility of the substance in the 
nose-fluid. 
Neither does the quantity of perfume present—so long as it is not insufficient— 
alter the odoriferous power. What one really smells, is a solution in air of the vapeur- 
forming body; and the strength of the solution is dependent on the vapour pressure 
and not on the amount of substance present. . 
_ Further Durrans mentions his theory on smell and free partial valencies. In cases 
where one molecule attracts the other, there are no free partial valencies at hand; 
and no smell arises. Sodium acetate is odourless, since the partial valencies are 
completely bound or, according to the Woker conception, since sodium is positive 
1) Cf. Report 1919, 104. — 7%) Perfum. Record 11 (1920), 12. — %) Cf. Reports Oct. 1904, 104; 1917, 117. 
— *) Cf. Report 1918, 112. — *) Cf. Report 1919, 107. — 4%) Perfim. Record 10 (1919), 266. — 7) Cf. Report 
October 1904, 104. : 
