Notes on scientific research. 95 



It has been demonstrated by experiments that carrots which had gently been brushed with 



leaves of different labiates, geranium species or garden rue, are not touched by animals. 



We should mention here further that essential oils can also serve, at least indirectly 



for the protection of wounds and for the prevention of undesirable loss of moisture 1 ). 



After M. Greshoff 2 ) had demonstrated some years ago that the common fern, Pterin 

 Aquilina, L, contains a glucoside which carries prussic acid, M. Mirande 3 ) has recently 

 made a similar observation on a fern which is frequently found in the mountains of 

 Savoy and in the Dauphine, Cystopteris alpina, Desv. (Cystopteris fragilis, Bernh., car. 

 alpina. Koch). The glucoside, which belongs to the amygdalin group and is contained in 

 the fresh green parts of this fern, liberates already in drying or when the leaves wither 

 prussic acid and benzaldehyde, in addition to other products. The quantity of glucoside 

 initially present in the leaves diminishes gradually in the course of the season. 



Physiological and Pharmacological Notes. 



In an article on odour and residual affinities, Th. H. Durrans 4 ) further discusses his 

 theory of smell to which we have already, alluded 5 ). We summarise once more the 

 main points of the theory of Durrans without going into the detail of the examples 

 which are no langer new. 



According to Durrans an odoriferous substance must (1) have residual affinities, 

 (2) be soluble in water and in the lipoid fats of the nose and must satisfy certain other 

 physiological conditions 6 ), and (3) be volatile. 



Not only the smell as such, but also the intensity of the smell will depend upon these 

 three conditions. If one of them be unfulfilled, the consequence may be absence of odour. 



Many facts support this theory of residual affinity. Bodies of similar type and 

 similar structure often have cognate odours. If the residual affinity be suppressed in 

 a molecule, its odour will be changed. This is observed among other things in the 

 reduction of ketenes to ketones and in the comparison between unsaturated bodies 

 and the corresponding saturated compounds. The position and distribution of the 

 residual affinities likewise plays an important part. The symmetrical diphenyl ethylene 

 has a strong floral scent, whilst l:l-diphenyl ethylene smells only faintly. Elements 

 which possess residual affinities, like oxygen, nitrogen, sulphur, phosphorus and the 

 halogens, form strongly-osmophoric groups; carbon and hydrogen, the affinities of 

 which are fixed according to Durrans (?) 7 ), do not. The osmophoric elements are also 

 near one another in the periodic table. When in an odorous compound the atoms of 

 partial valency are replaced by others, which do not possess any residual affinity, the 

 odour disappears likewise. From cacodyl would thus result the odourless ethane, 

 from methyl iodide methane. 



We take the following statements of interest for our special domain from a paper, 

 published by the German Board of Health written by E. Hailer, "Vergleichende Versuche 

 fiber die Einivirkung chemischer Mittel auf Kleiderlduse" (Comparative Experiments on the 

 Action of Chemical Reagents on Clothes-Lice) 8 ). 



Some 200 compounds of all classes of substances were tested as to the rapidity 

 and permanency of their action on lice. Thymol is among the substances which take 



x ) We should in this connection refer again to Oliver's theory of resin-formation, see p. 45 of this Report. 



— -) Report November 1908, 162. — 3 ) Compi. rend. 167 (1918), 695. — *) Perfum. Record 11 (1920), 391. — 

 5 ) Report 1919, 107. — 8 ) No details given. — 7 ) But carbon is not always credited with the same valency. 



— ") Arheiten aus dem Reichsges.-Amt 52 (1920), 312, 328. 



