TRANSACTIONS OF SECTION I. 793 



3. This method was modified as follows : — 



A steel spring, strongly clamped at one end, was arranged so that its free end 

 could be bent back to touch a hinged upright connected with a tambour; the record- 

 ing tambour was in connection as in method 2. By pulling on the spring by the 

 index-finger (the corresponding thumb being at the fixed point of resistance) the 

 vibratory movements ot tetanic muscles are communicated through the spring to 

 the air, and so to tLe recording tambour. The graphic representation of tliis is very 

 similar to that in 2. 



The figures in a typical set of tracings were 9, 6-G, 10,11", 14, 17, 13, 11-7, 

 18. The average of a large number of experiments was 12-5 vibrations per second. 



4. In this, the apparatus was as in 3, except tliat the myogram was taken on a 

 rotating cylinder, which also oscillated transversely seventeen times per second. 

 The tracing was in places identical with that obtained when one combines two 

 wave-systems whose periods are as 1 : 2 ; in other places there was a perfectly 

 simple wave-form. 



It is contrary to all we know to suppose that the tetanus had twice the rate of 

 the cylinder — viz. 34 ; the contrary must be true. 



If, then, the tetanus had at times a rhythm of 8'5 per second, and at times rose 

 to 17, the mean is 12'75. 



5. By a method employing a carbon resistance pile (upon which the muscle was 

 pressed) in the primary circuit of the inductorium, a capillary electrometer in the 

 secondary, and viewing the electrometer through a stroboscopic card, a rate of 12: 

 per second was estimated. 



6. By experiments with the microphone, on which the muscle was laid, the rest 

 of the connections being as in 5, the rate was fixed at 12-15. 



7. By the microphone laid over the contracting biceps, and a frog's gastro- 

 cnemius stimulated by secondary shocks (the microphone being in the primary 

 circuit of inductorium), a rate of 8-15 was estimated, or an average of 11'5 vibra- 

 tions per second. 



The average of these and very many other experiments is 12-5 per second. 



3. On Mirror Writing. By Professor F. J. Allen. 



4. On a Model of the Cochlea. By John G. M'Kendrick, M.D., F.R.S., 



Professor of Physiology in the University of Glasgow. 



Professor M'Kendrick exhibited a working moded intended to illustrate the 

 mechanism of the cochlea, devised by himself, with the aid of valuable suggestions 

 by Professor Crum Brown. It consisted of a water-tight glass tank divided into 

 two compartments by a horizontal glass diaphragm. At the end of each compart- 

 ment a round hole was cut and covered with an india-rubber membrane. The upper 

 hole represented the fenestra ovalis, and the lower the fenestra rotunda. The 

 horizontal glass plate had two holes cut, each of which was supplied with an india- 

 rubber membrane, and on each membrane there was a steel watch-spring tuned 

 to vibrate at a certain rate. The vibrations of the two springs were as 2 : 1. An 

 arrangement was used for imitating the movements of the stapes, consisting of a 

 rod caused to oscillate horizontally by an eccentric wheel. In this way pendular 

 vibrations were transmitted by the fenestra ovalis, and it was shown that when 

 the number of pushes made by the base of the stapes corresponded to the period of 

 spring A, spring A began to vibrate ; if the number of pushes was increased A ceased 

 to move ; and when the pushes reached the period of s, the latter began to move. 

 Finally, by an appropriate harmonic motion, the wave form of two vibrations of 

 2 : 1 was transmitted to the fenestra ovalis, and both springs vibrated when the 

 period of A was reached, thus showing that the apparatus analysed the compound 

 wave-form. The model generally supported the Ilelmholtz-IIensen theory of the 



