Odors and Flavors. 13 



lines as these we must search for an explanation of some 

 of the little understood points associated with the nourish' 

 meiit of hoth plants and animals. 



9. Ability to Recognize Small Quantities of Matter. We 



often marvel at the delicacy of the chemical balance and 

 many other instruments of measurement, but the delicacy 

 of the sense organs of men and animals, and particularly 

 the sense of smell, is so extreme that it is difficult *to form 

 a just conception of the minuteness of the quantity 

 of matter or of energy to which they will respond with the 

 degree of intensity which permits accurate judgments tQ 

 be formed. 



The sensations of odors result from the disturbances 

 produced on the organs of smell by molecules of different 

 substances moving through the air when brought to the 

 nose. But when the blind lady took the glove of a stranger 

 and, walking up and down the aisles of a large audience 

 room filled with people, handed the glove to the owner, 

 made known to her only by the likeness of the odor from 

 the glove to that escaping from the stranger, who will say 

 what fraction of a gram of that volatile principle it was 

 which produced so marked a sensation ? The weight of 

 volatile substance rising into the air from a man's track, 

 made by a shoe rather than his bare foot, must be very 

 small indeed, and yet the sense of smell in the dog is 

 so keen that he will follow his master at a rapid run even 

 when the tracks are two hours old and where many other 

 people may have passed along the same course more re- 

 cently than did his master. 



The readiness with which flowers, fruits and vegetables 

 may be identified by their odors alone, often at consider- 

 able distances, and with which animals scent their enemies 

 or their food, are all of them concrete demonstrations at 

 once of the extreme minuteness and vast numbers of mole- 

 cules, while at the same time they prove how sensitive is 

 the animal organization to such minute quantities of ma- 

 terial.' 



