ELEMENTARY VITAL PHENOMENA 



261 



and raises its temperature ; the latter can be read off upon a 

 thermometer projecting into the water. Various contrivances 

 serve to reduce the sources of error that depend upon possible loss 

 of heat. From the quantity of water and the warming of it in a 



Fig. 116^. — A portion of the galvanometer enlarged. The two columns sustain a compartment 

 within which is the ring-magnet in connection above with a small mirror ; the latter is sus- 

 pended in a case (outlined in dotted lines) by the silk fibre, and accompanies all the movements 

 of the magnet. (After Cyon.) 



FiQ. 116 y. — I. Arrangement of apparatus for thermo-electric measurement ; a, f, thermo-electric 

 needles, which are joined together on one side by the wire b, and on the other by the wire 

 &l ; & is coiled about the ring-magnet m having the north pole n. The magnet mis suspended 

 by a silk fibre c and fastened to a mirror a. In front of the ring-magnet is a straight magnet 

 Af, having the north pole N, at such a distance that the ring-magnet can still point toward 

 the north. An extremely slight cmrent suffices to cause it to deviate from its position. 

 In front of the galvanometer is a telescope F with a scale KK, the image of which the ob- 

 server 5 can see in the mirror s of the galvanometer ; thus he perceives every movement of 

 the mirror or of the ring-magnet by the shifting of the image of the scale. II and III. Dif- 

 ferent forms of thermo-electric needles, a, German silver ; /, iron. (After Landois.) 



definite time, the heat-production of the animal can be determined 

 with approximate exactness. In recent times the water- 

 calorimeter has been replaced by the air-calorimeter, in which the 

 cage containing the animal is surrounded by a closed air-chamber ; 



