HELMHOLTZ IN BERLIN 



the production of heat by friction, established, in a 

 comparatively rough way, the dynamical theory of 

 heat, in which heat is regarded as an accident or con- 

 dition of matter, a phenomenon produced by c a motion 

 of its ultimate particles.' 



Helmholtz studied the exchanges of matter that 

 occur in connection with muscular contractions, and 

 he made the important observation, that such ex- 

 changes are always accompanied by the disengagement 

 of heat. This indicated that animal heat, as produced 

 by a muscle, arises from the chemical phenomena 

 occurring in the muscle. Before this research, Mat- 

 teucci had apparently shown the production of heat 

 during muscular contraction by passing thermo-electric 

 needles into the muscles of a living warm-blooded 

 animal, and connecting the needles with a thermal 

 galvanometer ; but as in his experiments the blood was 

 flowing through the muscle, the proof that the in- 

 crease of temperature observed during the muscular 

 contraction was due to changes in the muscle itself was 

 not complete. Helmholtz got rid of the difficulty of 

 having to deal with an organ through which streams of 

 blood, possibly of different temperatures, were flowing, 

 by making observations on the isolated muscles of 

 c the old martyr of science,' the frog. He devised a 

 triple thermo-electric junction of iron and German 

 silver, so made that it could be passed through the 

 muscles of the thigh of a frog. A similar set of 

 junctions were kept at a temperature as uniform as 

 c 



