260 



GENERAL PHYSIOLOGY 



All measurements of temperature, whether by the thermometer 

 or the thermo-electric method, serve only to determine the 

 temperature that prevails in some one place in the organism at 

 some one time. They give no particulars regarding the quantity 

 of heat that the organism or the individual tissue produces. But 

 it is possible to determine the quantity of heat by investing the" 

 number of heat-units, or calories, that the living body gives off 

 to the outside in a certain time. Thus calorimetry has developed 

 by the side of thermometry. As is well known, a calorie is that 



Fig. 116 a. — Mirror galvanometer. Upon a board is an upriglit, supported by two colunins ; the 

 upper portion consists of a glass tube in whicli hangs a silk fibre suspending a ring-magnet 

 in the lower portion. At the two sides are two coils of wire. (After Cyon.) 



quantity of heat that is necessary to warm one kilogram of water 

 from 0° C. to 1° C. In order to measure the number of calories 

 that a living body, for example an animal, produces in a definite 

 time, the water-calorimeter has been constructed (Fig. 117). This 

 consists of a box having double walls that may be closed upon all 

 sides. The space between the two walls is filled with water, the 

 animal is placed in the box, and the whole is protected from 

 cooling or warming from the outside by a non-conducting covering. 

 The heat produced by the animal is communicated to the water 



