1444 
odorata, in which first exhaustion (adaptation) for a given odour 
was obtained, and directly after a measurement of smelling was 
taken. These experiments will be published in another paper. 
For terpineol, guajacol, caproic acid, I made tests in which, after 
complete exhaustion (adaptation), the smell-measurement was made 
in perfumed air, which of itself did not set up a smell-sensation 
any longer. 
In order to make a comparative estimate of the quantity of smell 
in the camera of 400 liters, I have determined, at the termination 
of my experiments, the minimum perceptibile in ZWAARDEMAKER’S 
smelling-box for the odour for which I had exhausted my sense-organ. 
I then found that for terpineol the just noticeable concentration 
was 3.9.10-10 erms. per c.c. of air. It is called. olfactie, so this 
definite small quantity of odourous matter per cc. represents the value 
of one olfactie of my individual unexhausted olfactory sense. At the 
commencement of the experiment the absolute quantity of odorivector — 
per ce. corresponding with the minimum perceptibile, was presumably 
smaller, seeing that my smelling capacity for the odours used had 
certainly decreased a little during my experiments. On this account 
the term “exhaustion” is perhaps more correct than “adaptation”. I 
will, therefore, use it for the present series of experiments *), although 
it should on the other hand be acknowledged that for the lower 
values the term is quite appropriate in connection with the constancy 
of the liminal values of differentiation and with the analogy to the 
sensation of light. (BACKMAN). 
After evaporation of one drop of terpineol the camera of 400 liters 
in which the head of the observer is enclosed, contains per cc. of 
air 5.10-® grms of odorous substance. This concentration represents 
125 of my olfacties as could be established at the termination of 
my experiments. [| remained in the perfumed air for 6 minutes. 
At the end of this period my olfactory sense had quite adapted 
itself to the condition, so that I was not aware of any sensation of 
smell. I did not perceive anything of the kind either when breathing 
deeply or when sniffing. 
1) Olfactometrical determinations showed that the obtusion for terpineol 
and guajacol was rather considerable at the end of my experiments, when 
compared with the beginning; for caproic acid, however, there was none. 
This may be inferred from the length to which the cylinder had to be moved 
out for the minimum perceptibile. It was: 
at the outset at the end 
tor terpineol 0.200 c.m. 0.300 c.m. 
for Suajacol 0.145 c.m. 0.300 c.m. 
for caproic acid 0.110 c.m. 0.110 c.m. 
