949 3 
immaterial whether the new sensation is looked upon as a mixed 
sensation or as a novel, individual one. Psychologically it seems to 
me e.g. that a combination of gaseous benzol and gaseous xylol 
yields one simple, unanalysable scent, though it contains an empyr- 
eumatic as well as an aromatic component. 
From these experiments it follows in the first place, that the 
combination of two odours, belonging to an homologous series, 
yields a smell-sensation even when each separate odour is subliminal. 
Distinct smell-sensations were generally obtained by me with two 
half stimulus-limina consequently by adding two half liminal values. 
Here then we have to do with a summation-smell. Two subliminal 
stimuli, belonging to the same homologous series are added and 
build up together a smell-sensation. This phenomenon may be looked 
upon as an analogue to summation-actions occurring in another field 
in physiology. The present writer e.g. observed some time ago, that 
some rest nitrogen-compounds of various chemical composition 
exert a distinct influence upon the heart and the blood-pressure 
through their analogous physiological action, even when injected in 
such small quantities that of themselves they are inactive '). 
The results of our combination-tests were to the following effect: 
Combination Cylinder-length Sensation 
‘Benzol-toluol-xylol 0.15—0.25—0.35 cm. | distinctly xylol-like 
| 0.07—0.12—0.17 „ | (none) 
Benzol-toluol-pseudocumol 0.15—-0.25—0.40 „ distinctly pseudocumol-like 
0.07—0.12—0.20 , doubtful, indistinct 
” ” ”„ 
Toluol-xylol-pseudocumol | 0.35—0.45—0.60 „ distinctly pseudocumol- _ 
xylol-like 
| 0.25—0.35—0.40 „ faintly pseudocumol-like 
0.20—0.45—0.50 , f a 
These combinations also substantiate our previous statement. In 
my judgment stimuli smaller than */, olfact do not build up a clear 
sensation. 
Lastly we subjoin some combination-tests with four smell-stimuii: 
(See following table p. 950). 
Also with these combinations every sensation is unitary. Still, in 
the first three groups the xylol-pseudocumol-scent supersedes. Sub- 
') E. L. Backman. Thesis. Upsala 1917. 
