1443 
cases of toxic anosmia evolved by cocain and in a case of post- 
diphterial anosmia. His results were distributed over two tables. In 
toxic anosmia evolved by cocain the smell of oil of camphor, of 
nutmeg, of Roman chamomile, of lavender and of laurel was un- 
impaired, whereas oil of thyme, tinctura nucis toncae, oil of euca- 
lyptus, of peppermint, oleum spicae, and oil of valerian was more 
or less obtused. Complete obtusion was attained with oil of cloves, 
of anise, of hyssop, of rosemary and with asafoetida. 
HERMANIDES’) examined exhaustion by taking for an index the 
lengthening of the reaction-time it causes and tabulated his results 
as follows: 
Lengthening of 
Reaction-time Constant Reaction-time 
After Exhaustion with 
Isoamylacetate } le Nitrobenzol 
Nitrobenzol ree Valerianic acid 
Valerianic acid deel Nitrobenzol 
Scatol Scatol Isoamylacetate 
Nitrobenzol 
Valerianic acid 
E. L. Backman’) objects to the idea of “exhaustion” and prefers 
the word “adaptation”, which, however, he also wishes to avoid, 
because he bases the whole phenomenon upon his differential- 
hypothesis. He assumes namely that a smell-sensation can be aroused 
only when a scent can penetrate as far as the olfactory cells in an 
increasing or decreasing quantity, but not when the accession 
of the odorous molecules (Hryninx’s odorivectors)*) occurs equably 
through invariable supplies per diffusion. The olfactory stimulus 
arises only when a certain procentic increase of the number of 
intruding molecules has taken place. From this hypothesis it follows 
that, with complete exhaustion (adaptation), only with a certain procentic 
increase of the concentration of the odorous matter in the air that 
reaches the olfactory region, a just noticeable sensation must be 
obtained. Backman’s hypothesis on this point has entirely been 
confirmed by my experiments conducted in ZWAARDEMAKER’s camera 
') HERMANIDES, J. Onderz. Physiol. Lab. Utrecht.. (5) Deel 10, p. 1. 
?) BACKMAN, E. L. Exp. Undersökningar öfter Luktsinnets Fysiologi. Upsala. 
Läkare förendings Föfhandlingar. N. T. Bd. 22, p. 319, 1917. 
°) Heyninx, A. Essai d’olfactique physiologique. These Bruxelles, 1919, p. 2. 
