No. I.] THE VERTEBRATE EAR. 295 



set in vibration, one having 512 vibrations per second, and the 

 other 100 vibrations per second. Each of these periods is rec- 

 ognized by the brain, as near as we can measure simultaneously, 

 as a distinct tone. Without, however, introducing any other 

 vibrating body into the experiment, we may, under proper con- 

 ditions, hear two other sounds, one of which we recognize as a 

 tone, the other as a sound. These two sounds are due to the 

 production of maxima and minima of stress, by the presence of 

 the two series of vibrations of periodicity 512 and 100 respec- 

 tively, journeying in the same direction through the air, but 

 with unequal steps. The tone is the same as that produced by 

 a fork having 88 vibrations per second, and the sound the 

 same as one having only 12 vibrations per second; and it is 

 found that these two sounds are produced by "beats" in the 

 two streams of sonorous vibrations. 



The ear may thus recognize at one time three distinct tones, 

 propagated through the same mass of air and endolymph. This 

 individual perception may be due to the presence in the hair 

 band of filaments which respond only to special wave lengths ; 

 it may be due to the successive response of all the hairs to all 

 the varying stresses of the uneven stream, as illustrated by a 

 wheat-field in a gusty wind ; or it may be due to a combination 

 of both these factors ; and to the latter view I incline, giving 

 preponderance to the second condition. 



Analysis of sound (or sound waves) is then, according to my 

 conception of the auditory function, a process which does not 

 occur in the way in which it has been previously supposed to 

 take place. From a study as complete as we can yet make 

 it, the auditive process is seen to be so different from the 

 Helmholtz-Hensen conception that the use of the word analysis 

 is not admissible. There is in reality never an analysis, either 

 in the end organ or in the central apparatus ; but each external 

 physical variation that succeeds in producing an alteration of 

 the end organ (practically superficial, i.e. lying on the bounds 

 between the mass of the sentient matter and the external) is 

 propagated simply, it may be in more or less converted form, 

 but still a direct and continuous transmission of a variation of 

 previous relations of external matter. While journeying in com- 

 pany with other undulations, a sonorous undulation is subject, 

 not only to change, but to annihilation as well. Only after 



