Rouse, Respiration in Pigeons. 499 



and, being less sensitive, to execute the inspiratory, or active, 

 part of the respiration a little less quickly, thus relatively short- 

 ening the expiration. 



The absolute breathing rate varied considerably from day 

 to day, and sometimes even during an experiment. In case of 

 the above animal the average was 33.6 per minute, though 

 some other pigeons showed a considerably lower rate. 



III. General Respiratory Reactions. 



/. Acoustical. It was soon noticed that the breathing 

 was sensitive to sounds in the room, especially to those which 

 came from the cages (cooing, flapping, and the like). The reac- 

 tion given to the sound of the bell was principally a quickening 

 and shallowing, ^ these alterations increasing for a time after the 



Fig. J. Reaction to sound of bell. The break in the second line indicates 

 the duration of the stimulus. 



end of the stimulation (see Fig. 3.). A pistol shot would result 

 merely in a short pause or temporary hesitation in breathing, 

 followed by a slight quickening of rate. The animal readily 

 became accustomed to these artificial stimuli, and reacted less 

 and less vigorously to them. Yet the sounds which proceeded 

 from the cages in the same room never lost their stimulating 

 effect, perhaps because of their significance. A few instances 

 were noticed in which the reactions seemed to be conditioned 

 by the simultaneous occurrence of a sound stimulus to which 

 the animal was thoroughly accustomed and therefore insensi- 



'Lehmann, a. KSrperlichen Aeusserungen psychischer Zustande. Leipzig^ 

 1899. 



James, W. Principles of Psychology, II, 372-382. New Vork, 1890. 



