METABOLISM 



it is interesting to note thai the actual heal given ou1 when a definite 



amounl of alcohol or ether is burned in 01 E them exactly corresponds 



t(. the amounl as measured by the smaller bomb-calorimeter. All of the 

 energy liberated in the body does not, however, take the form of heat. A 

 variable amounl appears as mechanical work, so thai to m< • in calo 

 fill of the energy thai an animal expends, cne must add to the actual cal- 

 ories given out. the calorie equivalenl of the muscular work which has 

 been performed by the animal during the period of observation. This 

 be measured l>\ means of an ergometer, a calorie corresponding to 

 kilogram* meters of work. That it has been possible to Btrike an accui 

 balance between the intake and the outpul of energy of the animal body, 

 in one of the achievements of modern experimental biology. It call be 

 done in the case of the human animal ; thus, a man doing work on a bicycle 



ergometer in the Benedict calorimeter gave ou1 - ctual heal 4,833 I 

 and did work equalling 602 C, giving a total of 5,435 C. By drawing up 



a balance sheet of his intake and output of t 1 mat. -rial during this 



period, it was found that the hail consumed an amounl capable of 



yielding .~>.4.~>!) < '.. which may be considered as exactly balancing the actual 



olltpUt. 



It would he out of plaee to give a full description of the respiration 

 calorimeter here. The general construction will be seen from the accom- 

 panying figure of the form of apparatus iu use for patients in the Russell 

 Sage Institute. New York. <>ne of the most interesting details of ita 

 struction concerns the means taken to prevenl any l"ss of heat from the 

 calorimeter to the surrounding air. This is accomplished in the following 

 way: Tie innermosl layer of the wall is of copper; then, separated from 



this by an air space, is another wall of copper, outside of which are two 

 wooden walls separated from each other and from the outer cupper walls 



by aii- spaces. The tw >pper walls are inected through thermoelectric 



couples, so that an electric current is set up whenever there is any dif 



elice ill their temperatures. The current is ohseiwed by means of a gal- 



vanometer placed outside the calorimeter, and from its movements the ob- 

 server either heats up or cools down the outer copper walls - - ■ 



reel the difference of temperature causing the current. This is done hy an 

 electric heating device or by cold water tubes placed between the oul 

 most copper and tin- innermost wooden wall- Since the temperatur< 



the two copper walls is the same, there can he no exchange of heat het w 



them, and consequently none of the heat that is absorbed by the inner i 

 per walls is allowed to he carried away. All the heat given out by the 

 animal is absorbed by the stream of cold water flowii >ugh the coils 



Igh \\ lii< ! 



