304 Dr. A. D. Waller. Effect of Heat upon the [Feb. 20, 



A sartorius muscle led off to the galvanometer in the usual way. A 

 platinum wire adjusted transversely under one of the electrodes A or B 

 of an accumulator, a metronome key and a hand-key K, all in the same 

 circuit, so that the metronome gives regular brief periods of closure (when 

 the hand-key is also closed) that raise the platinum wire to a red heat for 

 a fraction of a second. The glowing wire heats the muscle locally at A by 



radiation and by the ascending current of heated air. The heat is graduated 

 by bringing the wire nearer or farther from the muscle, or by varying the 

 number of effective closures, or by varying a resistance in the accumulator 

 circuit. It can be calculated if required. But the important condition to be 

 secured is not so much an accurately known amount of heat as an accurately 

 repeated application of a definite regular amount of heat. In these experi- 

 ments the heat at each glow of the wire amounted to 0*08 calorie. 



The movements of the muscle are recorded by a lever on the smoked 

 cylinder or plate. The movements of the galvanometer mirror indicative of 

 the electrical changes are at the same time recorded photographically. 



Result : — 



Moderate heat at B gives current in the muscle from A to B. 

 Excessive heat at B gives current in the muscle from B to A (= a current 

 of injury). 



After which moderate heat at B gives hardly any effect, because B is 

 injured. 



Dead (i.e. heat-rigored) muscle gives small effects in the same direction, 

 that are ordinary physical (thermo-electric) effects. 



The results on muscle are nearly quite satisfactory, the only drawback to 

 their absolutely conclusive character is this small residual positive effect in 

 the same direction as the ordinary thermo-electric currents from the heated 

 .side. But as will be understood from the consideration of skin effects, even 



