1892.] On the Mechanism of the Closure of the Larynx. 323 



rate of rotation, while with the single hole the puff, though distinctly 

 audible, remained the same monotonous sound, independent of 

 sudden variations of the speed of the disk. The only change in 

 character was that the intensity diminished with the lower rates of 

 vibration. 



From the foregoing, we have been led to the following conclusions : 



1. When sound is produced by a vibrating body, each individual 

 wave of the series causing the tone stimulates the terminals of the 

 auditory nerve. If the single vibrations are of such a nature as to be 

 inaudible, no tone can be heard. 



2. The individual vibrations can be heard when the rate of vibra- 

 tion is too slow for a distinctive tone to be appreciated. 



3. The immediate succession of two waves, at rates of vibration 

 above fifty per second, gives rise to a sensation of tone having the 

 same pitch as that yielded by a prolonged series at the same rate. 



That is to say, one can distinguish the tone produced when only 

 two vibrations of a series reach the terminals of the auditory nerve. 



4. Having worked for some time with rates of vibration near the 

 limit of the lowest tones, we are forced to admit that we have not 

 attained the skill (said to be attained by practice) of distinguishing 

 small changes in pitch with rates of vibration below fifty per second; 

 at least, in the case of pendular vibration, such as is produced by 

 tuning forks or muscular contraction. 



II. ' On the Mechanism oi the Closure of the Larynx. A Pre- 

 liminary Communication." By T. P. ANDERSON STUART, 

 M.D., Professor of Physiology, University of Sydney, 

 N.S.W., Australia. Communicated by Professor E. A. 

 SCHAFER, F.R.S. Received December 10, 1891. 



By a series of papers ending with that by mysfelf with Dr. A. 

 McCormick (' Journ. Anat. Physiol.,' January, 1892), it has been 

 finally determined that the time-honoured doctrine of the closure of 

 the larynx by a lid-like action of the epiglottis is quite untenable ; 

 but, so far as I am aware, no satisfactory account of how after all the 

 larynx is closed voluntarily and reflexly has as yet been given. The 

 determination of the positive side of the question was nevertheless 

 the necessary sequel of the determination of the negative side ; 

 having settled how it is not closed, one naturally proceeded to enquire 

 how the larynx is closed, since closed it at times must be, and that at 

 its very entrance. 



In the literature of the subject I find that there is considerable 

 looseness of diction. " Closure of the larynx " may mean either 

 " closure of the glottis," " closure of the vestibule," or " closure of 



