166 A RESPIRATION CALORIMETER. 



The number of revolutions of the pedal of the ergometer is recorded 

 on the observer's table by the cyclometer shown in figure 48, which is 

 designated as the Dinsmore electric counter, since it was devised by our 

 mechanician, Mr. Dinsmore. 



This instrument consists of an electro-magnet and armature, the 

 latter having a projection which extends to the ratchet wheel of the 

 cyclometer. A device on the crank wheel of the ergometer closes a 

 circuit to the magnet at each revolution, and thus actuates the armature. 



Correction for the magnetization of the fields of the ergometer. In work 

 experiments with the ergometer a correction of the heat measured by 

 the calorimeter is necessary because of the heat added to the chamber 

 in magnetizing the fields of the ergometer. The amount of heat thus 

 added varies with the strength of current. 1 For the strength generally 

 employed, namely, 1.25 amperes, it amounts to 10.94 large calories per 

 hour, which is accordingly deducted from the heat measured. 



BLANKS USED FOR HEAT RECORDS. 



A specimen page from the calorimetric records, showing the printed 

 blank in use in the heat calculations, with observations for a portion of 

 an actual experiment recorded therein, is given on page 167. For a 

 clear understanding of this sheet, reference to figure 43 is also necessary. 



It will be noted that at the top of the sheet are recorded the date, the 

 number of the experiment, and the name of the observer. Then follow 

 ten vertical columns, in which are inserted the various readings for one 

 hour. A space at the bottom of the sheet allows for further observa- 

 tions if necessary. 



In the first vertical column is inserted the time of each reading. It 

 is so arranged that these may be recorded every two minutes, though as 

 a matter of fact it has been found that in ordinary rest experiments 

 four-minute readings are sufficient, except at periods of increased bodily 

 activity, as at 7 a. m., when the subject is dressing and carrying out 

 the somewhat extensive routine elsewhere outlined. At such times 

 certain readings are recorded every two minutes as long as vigorous 

 activity continues. 



The second column is headed " Inner walls, No. i." In this are 

 recorded the deflections produced by pressing down the key marked 

 A Iy I, No. i, in figure 43. The third column gives similar readings 

 for the incoming air current, as shown by key No. 2, and the fourth 

 the deflections for the outer walls, as indicated by the key marked 

 A Iy L No. 3. The readings obtained from these three keys are recorded, 



1 The calculation is made according to the formula C X E X I X 0.2385 = calories. 

 See page 172. 



