( 714 ) 



are \isil)le wliicli admit of no oilier explaiialion than that llio motion 

 of the wire, lepreseiiliiig tlie sunnd in its fniidameiital and partial 

 tones, consists of a nnniher of vibrations of different frequencies 

 and amplitudes. 



We hope soon to analyse this phenomenon photographically. When 

 the intensity of the sonnd is changed, the hreadtli of the grey band 

 also changes imniediately. And at the moment the sonnd stops, one 

 sees the narrow, black image of the ^vire standing perfectly still 

 again in the bright field. 



When the telephone is replaced by a microphone and a suitable 

 induction-coil, the same phenomena are observed; with these contriv- 

 ances however the arrangement has become much more sensitive. 

 Feeble sounds now give rise to considerable broadening and it is 

 surprising to see, how, when one speaks softly at a distance of one 

 or more metres from the microphone, the image of the wire reacts 

 powerfully on each word that is spoken or raiher on each syllable 

 that is pronounced, luit always immediately occupies its position of 

 rest as soon as the sonnd stops for a iiKmient. 



Feeble sounds, as e.g. the cardiac sounds of a rabbit are excel- 

 lently rendered by the galvanometer. 



Besides for the study of phonetics and of cardiac sounds, the wire- 

 galvanometer will liud fruitful aj>|ilication.s over an extensive range 

 of physiological research. We already communicated some results of 

 an investigation coiu'erning the human elect rocardiogrcim ^j. Besides, 

 an investigation of the nerve-currents is now in course of progress, 

 about which we will oidy meiuion in this place that the action- 

 currents of a nerve, resulting upoji simple stimulation, can be shown 

 and registered in an excellent manner. As far as I know action- 

 currents of the ischiadic of a frog, arising by the stimulus at the make 

 and break of an ascending aiul of a descending constant current, have 

 never been observed hitherto. The string galvanometer shows them in 

 all their details as they nuist be expected according- to Pflüger's law 

 of contractions and the existence of which could until now only lie 

 surmised from the observed muscular contractions. One also sees the 

 superposition of the phenomena of electrolonus on those of the action- 

 current, which need be no impediment to the interpretation of the 

 obtained curves. We seem to be justified in supposing that perhaps 

 new points of view will be opened about the manner in which the 

 nerve is capable of reacting on various stimuli. 



ij 1. c. 



