THE SENSE OF SMELL IN BIRDS 639 
writer's judgment, to less tractable birds whose habits might 
suggest greater olfactory possibilities. During the series of ex- 
periments there were many occasions when even these birds were 
none too manageable. 
Choice of odor. An ideal odorous material for these experiments 
should be associated with the natural food-seeking habits of the 
subject. It should also stimulate only the olfactory sense or- 
gans. Unfortunately, the first condition could not be realized, 
and the second could not be established with absolute certainty. 
A eareful consideration of food materials did not suggest any- 
thing under practicable conditions which would supply a strong 
odor as measured by the human olfactory organs. No odorous 
material of any kind could be found where the possibility of other 
than olfactory stimulation could be known to be absolutely elim- 
inated. It was therefore necessary to consider odors which do 
not have any known relationship to the experience of ring-doves. 
The following were selected as being the least objectionable: 
animal musk, violet-sachet powder, and oil of bergamot. Eau 
de cologne was used for the first series of experiments, but it was 
finally abandoned as the writer became impressed with the possi- 
bility of alcohol stimulation by the alcohol contained in this 
compound. Animal-musk and violet-sachet powder when they 
were not dissolved in alcohol produced odors so weak that they 
were employed only a short time. <A strong odor seemed desir- 
able because these birds could not be assumed to have so keen a 
sense of smell as even man possesses. Oil of bergamot was finally 
chosen for the larger portion of the work because it seemed to 
combine strength with freedom from at least apparent danger of 
there being other than olfactory stimulation. In the absence 
of knowledge concerning the effects of odorous materials upon the 
dove’s sense organs, the sensations of the experimenter could be 
the only guide in choosing an odor. It may be objected that 
when held very near the nose, oil of bergamot produces almost 
painful sensations, which may involve tactile endings. Under 
the conditions of the experiments, however, the stimulation of 
olfactory endings was mild for the writer and there were no sug- 
gestions of any other stimulation. 
