950 
Sea ee SS eS EED 
Combination Cylinder-length Sensation 
Benzol-toluol-xylol-pseudocumol 1.80—3.00—4.20—4.80 cm. | Mixed scent of ben- 
zol-toluol and xylol- 
pseudocumol. The 
latter superseding. 
Benzol-toluol-xylol-pseudocumol 1.20—2.00—2.80—3.20 cm. Mixed scent of ben- 
zol-toluol and xylol- 
pseudocumol. The 
| latter superseding. 
Benzol-toluol-xylol-pseudocumol | 0.15—0.25—0.35 -0.40 cm. | Mixed scent of ben- 
| | zol-toluol and pseu- 
| documol. The latter 
superseding. 
| 
Benzol-toluol-xylol-pseudocumol « 0.07 — 0.12—0.17—0.20 cm. | (none). 
| 
liminal stimuli, when combined, build up an accumulative sensation 
here also. We conclude therefore: The combination of two or more 
subliminal quantities of substances of an homologous series gives rise 
to a distinct accumulative odour. 
It is very difficult to say whether a similar summation occurs 
also with superliminal quantities, though to me it does not seem 
improbable. 
The Compensation tests. 
Initially one of the olfactometrical cylinders of the double olfacto- 
meter was moved out a little to obtain a stimulus of 6 olfacts. 
Subsequently a small amount, followed by a larger one, of another 
substance was added and the smell-sensation was observed. The 
determinations were made at intervals of various lengths and were 
repeated several times on the same and on successive days. In the 
interval between two tests the cylinders were pushed hard up against 
the sereen to obviate excessive volatilization or to balance the 
diffusion-difference within the cylinder where, otherwise, the intensity 
of the upper iayers of the odorous substance would be reduced. We 
still wish to call attention to the fact, that the results obtained one 
day were invariably found back on the following day. 
.Generally speaking we found that by keeping the amount of one 
substance constant, and allowing the other to increase, also the 
smell-sensation passes gradually from one odour into the other, but 
that there will always be a field in which the two odours weaken, 
nay even cancel each other. On the whole, therefore, complete 
compensation of the sensations is obtained by mixing carefully 
apportioned quantities of odorous substances. 4 
