286 Journal of Comparative Neurology and Psychology. 



ations on sense-organs, nerve cutting and like methods may aid 

 us in determining what organ or portion of an organ is neces- 

 sary for a particular function, but they can give us no trust- 

 worthy information concerning the relation existing between the 

 senses and the normal behavior of the animal. Therefore, in 

 the experiments now to be described, with the exception of 

 those which were made to ascertain whether the ear is necessary 

 for reaction to sounds, normal frogs were studied either in their 

 native haunts or in the laboratory. All the detailed work was 

 done with the green frog, Rana clainitans, but tests were made 

 also with the leopard frog, R. pipiens, and the bull frog, R. 

 catesbiana. 



II. Reactions of Frogs in Nature to Sounds. 



My attention was first drawn to the subject of frog audition 

 by failure to obtain motor reactions to sounds in an investiga- 

 tion of the time relations of the neural process of the green frog. 

 Although a large number of sounds of different qualities, pitches 

 and intensities were employed, no visible motor reactions were 

 observed. This led me to seek the significance of what ap- 

 peared to be either a surprising lack of sensitiveness to changes 

 in the environment which would naturally be expected to 

 stimulate the animal, or an interesting and important case of 

 the inhibition of reaction to auditory stimuli. The question to 

 be answered is, Are frogs deaf, or do they under certain con- 

 ditions completely inhibit their usual reactions to sound ? 



Since they bear upon the question of deafness I quote the 

 following observations on the influence of sounds in Nature from 

 the auditory-reaction section of my earlier reaction-time paper. ^ 



In order to learn how far fear and artificial conditions were causes of the in- 

 hibition of responses to sounds in the laboratory, and how far the phenomenon 

 was indicative of the animal's inability to perceive sounds, I observed frogs in 

 their native haunts. 



By approaching a pond quietly, it is easy to get within a few yards of frogs 

 sitting on the banks. In most cases they will not jump until they have evidence 



^The Instincts, Habits and Reactions of the Frog. Harvard Psychological 

 Studies, 1, 629-630 {Psychological Review Monogy-aph, 4), 1903. 



