IV 



THE SENSE OF SMELL 



183 



odours, but generally assumes the more or less definite characters 

 of partial anosmia. 



A methodical study of this interesting subject might show the 

 best way to solve the problem of the classification of odours 

 according to their specific energies. But the results so far 

 obtained have not corresponded with these expectations. 



Among the experimental researches in this direction, those of 

 Frohlich and of Aronsohn promised important results. Both 



Olfaaies 



20 30 



SO 



90 



FIG. 70. -Curve of olfactory fatigue. (Zwaardemaker.) The liminal values are marked in olfacties 

 on the ordmates ; the duration of stimulation in seconds on the abscissae. The four 

 curves (two of caoutchouc of 10 and 14 olfacties ; two of benzoin of 3.5, and 9 olfacties) show 

 a more or less marked rise in the liminal value after successive stimulations of increasing 

 duration. The length of the olfactory stimulations is regulated by a metronome which marks 

 seconds. The subject takes a deep breath every two seconds. 



fatigued their sense of smell by a special odour, and then sought 

 to determine the odours for which olfactory sensibility was still 

 normal, or had been diminished to the same extent as for the 

 odour experimented with. Theoretically, different specific energies 

 must be assumed for the first, and identical energies for the 

 second. 



Frohlich's researches led to no unequivocal practical con- 

 clusions ; Aronsohn 's, on the contrary, while carried out by a less 

 exact method (he took no account of the intensity of the different 

 odours) led to some results that deserve mention. He found that 



