SENSATIONS AND THE SENSE-ORGANS 145 



sense of smell, lagging far behind many of the animals 

 with their power to trail their mates and their prey. 

 It can be shown by microscopic study that in such 

 animals the olfactory nerves have notably extended 

 connections within the cerebrum. Still it is probably 

 true that the human endowment is superior in some 

 respects. We can appreciate more varieties of so-called 

 flavor (really odor) than cats and dogs can discriminate. 

 We do not seem to be able to discover a weak odor in 

 the presence of a strong one. A dog tracking a rabbit 

 through a growth of sweet fern seems to do just this 

 thing. Yet it may be that the odor of the rabbit is 

 stronger for the dog than the fragrance of the herbage. 



All sensations diminish more or less if the exciting 

 stimuli are long continued. This kind of fatigue is 

 marked in the case of smell. Most odors cease to be 

 perceptible if the substance responsible remains with 

 us. People who have been for some time in a room 

 which has become close, or where vegetables are being 

 cooked, may not notice odors which are very apparent 

 to a newcomer. Our judgment as to whether odors 

 are good or bad is closely linked with our theories of 

 their origin. An aroma which might be thought ap- 

 petizing when proceeding from a cheese would de- 

 cisively condemn an egg. 



Attention may be called to the probable influence 

 of the erect position upon the relative importance of 

 the sense-organs. An animal roving about with its 

 nose close to the earth is in a stratum of air laden with 

 odors. These rapidly diminish in variety and intensity 

 with elevation. The human nose is carried at such a 

 height that there are comparatively few sources of 

 stimulation for it. But the same lifting of the head 

 above the ground has somewhat extended the range of 

 hearing and vastly widened that of vision. 



Hearing. It has been said that when we taste .any- 

 thing we realize its close contact with a special part 



of the body surface. When we smell anything there is 



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