Rouse, Respiration in Pigeons. 513 



much less than do mechanical stimuli. The reaction usually 

 involves an immediate quickening of rate, varying with the color 

 of the light, and occasionally diminutions of amplitude and 

 minor irregularities of contour. 



4. Since an agreement was found between the color-pref- 

 erences and the increase in breathingrate caused by colored light, it 

 would seem that agreeable feelings are accompanied by respiratory 

 quickening (and perhaps by shallowing and irregularity). 



5. Daily reactions of four birds to three intensities of 

 light, one intensity per day, showed no direct relation between 

 amount of stimulus and amount of reaction. The second daily 

 reaction showed the influence of repetition, since considerably 

 weaker than the first ; but thereafter was seen a continuous in- 

 crease in amount of response. 



6. Meaningless stimuli, as pistol shots, quickly lose 

 their disturbing influence upon respiration, although it remains 

 sensitive to those of a significant character, such as noises made 

 by other birds. A stimulus which no longer influences the 

 breathing, will sometimes occasion disturbance if accompanied 

 by a second stimulus, of another order, even though of weak 

 intensity. 



