Sensory Discrimination: The Chemical Sense 113 



The hypothesis has been put forward by Cyon (165) that 

 smell may somehow function in guiding the long flights of 

 birds. Watson (770) found that the noddy tern could 

 find its way from Key West to its nest on the Tortugas 

 with the nostrils tightly sealed. Strong, however, points 

 out that this bird has very small olfactory organs, and 

 thinks it possible that other birds may make more use of 

 the olfactory sense in homing and migrations. The ful- 

 mar, for instance, is a bird which makes very long ocean 

 flights, and has an enormously developed olfactory appara- 

 tus. Strong (696) made experiments with the ring dove 

 in which he was apparently able to establish some asso- 

 ciation between the smell of bergamot in a certain compart- 

 ment and the choice of that compartment as containing 

 food. 



When we come to the Mammalia, we find in the great 

 majority of types a very high development of qualitative 

 discrimination in the sense of smell. Hunters know it to 

 be the chief defensive weapon of wild animals, and it has 

 retained great keenness in many domesticated ones, the 

 cat, for instance, which will be awakened from slumber in 

 the garret by the odor, quite unsuspected of human nostrils, 

 of some favorite food being prepared in the kitchen, and is 

 thrown into ecstasy at a faint whiff of catnip. The dog, 

 however, is the hero of this field of mental prowess. The 

 experiments of Romanes on the power of a favorite setter 

 to track his scent are well known. In one of them he col- 

 lected a number of men, and told them to walk in Indian 

 file, "each man taking care to place his feet in the footprints 

 of his predecessor. In this procession, numbering twelve 

 in all," Romanes says, "I took the lead, while the game- 

 keeper brought up the rear. When we had walked two 

 hundred yards, I turned to the right, followed by five of 



