ANIMAL MECHANICS. 



17 



regular motion, until he made the sound so produced to coin- 

 cide roughly with that of the muscular contraction ; and he at- 

 tempted to estimate the number of notches passed over in a 

 second. His conclusion from these comparative experiments 

 is the following : — 



" The greatest frequency that I think I have observed was 

 about 35 or 36 in a second, and the least was as low as 14 or 

 15 . . .; they appeared to be in general between 20 and 30 

 in a second ; but it is possible that the method I employed 

 may be found defective, and it is to be hoped that my estimate 

 may be corrected by some means better adapted to the deter- 

 mination of intervals that cannot actually be measured." 



An accidental observation made upon myself in the early 

 part of 1862, enabled me to fix with the precision desired by 

 Wollaston the rate of the muscular contraction that causes the 

 susurrus. In December, 1859, on recovering from a fever, 

 which I acquired from an English patient under the care of 

 Dr. Jonathan Osborne, in Sir Patrick Dun's Hospital, I found 

 that it had left the following trace of its visit in my system : — 

 Occasionally since that period, when overworked by mental 

 exertion, I have been subject to a singing in both ears, which 

 is relieved by a drink of warm milk, and by sleep ; sometimes, 

 however, I have found the tinnitus aurium so great as to pre- 

 vent sleep. 



In June, 1862, while kept awake by this disagreeable 

 noise, I amused myself with producing, by the contraction of 

 the masseter muscles, their well-known susurrus. To my great 

 surprise and pleasure, I observed that the tinnitus and susurrus 

 were in unison, differing from each other by several octaves. 



I followed up the clue thus found, and consulted my mu- 

 sical friends, whom I instructed in the mode of making Wol- 

 laston's experiment, without, however, informing them of the 

 note that I myself believed to be the true sound of the susur- 

 rus and tinnitus. My friends have arranged themselves into 

 c 



