186 



PHYSIOLOGY 



CHAP. 



Valentin experienced this on smelling ether and balsam of 

 Peru at the same time. He concluded that there was a conflict 

 between the two olfactory sensations analogous to that observed 

 in the two visual fields, according as attention is fixed on one or 

 other of them. The same olfactory conflict was noted by Aronsohn 

 between the smell of camphor and that of cedar oil. 



In other cases there is no such conflict on stimulating the 

 olfactory sense by two odours at the same time, nor does the 



FIG. 71. Zwaardemaker's double olfactometer with porous tubes. Its construction is the same 

 as that of the simple olfactometer (Fig. 69). The two olfactometers are separated by metal 

 diaphragms, and run on two rods marked in centimetres. The ends of the olfactometer tubes 

 are introduced into the two nostrils, when two different odours are simultaneously employed. 

 Or they may be united by the T-tube shown in the figure, so as to stimulate only one nostril 

 simultaneously with both odours. 



stronger smell predominate ; but there is a more or less perfect 

 neutralisation, and the two odours become fainter or disappear 

 entirely. Thus Aronsohn saw that the smell of camphor dis- 

 appeared on simultaneously smelling petrol, eau de cologne, 

 essence of juniper, or garlic, though all these odours are weaker 

 than that of camphor. 



Zwaardemaker made a scientific study of these neutralisation 

 effects. For this purpose he employed his double olfactometer 

 (Fig. 71). With this instrument he was able to apply a different 

 odour of measurable intensity to each nasal fossa by introducing 



