ELEMENTARY VITAL PHENOMENA 



259 



galvanometer (Fig. 116) the magnet has the form of a ring which 

 is suspended by a silk fibre in the space within the coil ; a small 

 mirror is connected with the ring and accompanies all the move- 

 ments of the latter (Fig. 116 /3 7). At some distance from the 

 apparatus stands a telescope bearing a scale, the image of which 

 by careful adjustment can be observed through the telescope in 

 the mirror of the galvanometer (Fig. 116 7). The slightest 

 deviation of the ring-magnet is shown in the telescope by a 

 shifting of the image of the scale. According to the extent of 

 this shifting the strength of the electric current can be computed, 



FIG. 115. Multiplier. /, Plan. An astatic system, with the north poles N and N', is suspended 

 upon a silk fibre G. Around the lower needle is a coil of wire W ; the upper needle moves 

 above a graduated disc. (After Landois.) //, Multiplier complete. (After Cyon.) 



and hence empirically the amount of heating of the thermo- 

 electric element, or, better, a whole series of thermo-electric 

 elements. Thus the most delicate changes of temperature that a 

 living tissue undergoes can be determined. By investigations of 

 this kind it has been established that a higher temperature is pro- 

 duced by greater activity of the cells of a tissue, e.g., a gland or 

 a muscle, than by less activity or during rest. This result is in 

 close accord with our ideas concerning the production of heat, for 

 the greater activity of the cells depends upon a greater metabolism 

 in them, and heat results from chemical transformations in the cell. 

 It is an old experience that one can warm himself by vigorous 

 muscular activity. 



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