Dr. Alison on the Differential Stethophone. 385 



these organs is not observed till after six hours and more, that is to 

 say, when the muscles have been preserved in a temperature of 14° 

 to 16° R. In a temperature of 4° to G° R., the irritability of the 

 poisoned muscles may last for double this time, as is usual with all 

 poisoned muscles and nerves ; but even in this case it disappears 

 long before that of the non-affected muscles. 



4. If muscles which have lost their irritabihty through the Tang- 

 hiuia are put into a solution of common salt of from i to 1 per cent., 

 their power of contraction reappears after a certain" time, but only 

 when they have been preserved at the lower temperature of 5° to 6° R, 



5. Lastly, the nerves also are ^ffr«/y5erf by the Tanghmia, and, as 

 far as we were able to pursue this question, under the same circum- 

 stances as the muscles, only perhaps a little earlier. 



From all this it follows that the Tanghinia is a paralysing, and 

 above all, a muscular poison. As far as we have been able to follow 

 its action, it resembles very much, the Upas Antiar ; only its power 

 would seem to be a little less strong. 



April 22. — Major-General Sabine, Treasurer and V. P., in the Chair. 



The following commu.nication was read : — 



" On the Differential StethophonCj and some new Phenomena 

 observed by it." By S. Scott Alison, M.D. 



Engaged for some years in investigations into the phenomena of 

 audition, I have become cognizant of some facts which I believe have 

 hitherto remained unnoticed, and which are certainly not generally 

 known to physicists and physiologists. 



The first of which I shall treat is the restriction of hearing 

 external sounds of the same character to one ear, when the intensity 

 is moderately, yet decidedly greater in one car than in the other, the 

 hearing being limited to that ear into which the sound is poured in 

 greater intensity. The sound is heard alternately in one ear and in 

 the other, as it is conveyed in -increasing degrees of intensity, and 

 hearing is suspended alternately in one ear and in the other, as the 

 sound is conveyed in lessening degrees of intensity. 



Sound, as is well known, if applied to both ears in equal intensity, 

 is heard in both cars ; but it will be ibund, if the intensity in respect 

 to one ear be moderately yet decidedly increased, by bringing the 

 sounding body nearer that car than tlie other, or otherwise, as by the 

 employment, in respect to one ear, of a damper or obstructor of 

 sound, or in respect of the other ear, by the em]jloynient of some 

 intensifier, or good collector or conductor of sound, the sound is heard 

 in that ear only which is favoured and has the advantage of greater 

 intensity. 



There is little doubt that this law holds with regard to sounds 

 passing through the air, and carried to the ear in the ordinary 

 manner, without the aid of any mechanical contrivance, as for in- 

 stance those of a watch placed in front of the face ; but as the re- 

 striction of hearing to one ear, and its snpjjression in the other, 

 admit of being rendered more obvious ))y an aj)])aratus that shall 

 collect sound, prevent its diffusion through the air, and carry it 



Pkil. May. S. 4. Vol. 10. No. 108. Nov. 1858. 2 C 



