r>(\2 STATE BOARD OP AGRICULTURE. 



It will be noticed at once that the percentage of nitrogen was higher 

 at the end of the experiment than at the beginning. As is apparent 

 also, the oxygen used was greater than the carbon dioxide given off. 

 Now, this latter fact would decrease the volume of gas with the in- 

 sects; and that decrease, alone, would cause the percentage of nitrogen 

 to rise, if the cubic centimeters of that gas present remained the same. 

 (As will be proven later, the amount of nitrogen is not appreciably 

 diminished or increased by an insect during respiration.) Indeed, it 

 must be evident that a decrease in volume due to an absorption of one 

 or more components in a gas-mixture must be accompanied by a pro- 

 portional increase in the percentage of all other components. If, for 

 a single gas component then, the ratio of increase be found, it would 

 be known for all the rest. Since, in air confined with respiring insects, 

 the volume of nitrogen remains unchanged, the ratio of its percentage 

 at the end of the experiment to its percentage at the beginning must be 

 (he desired ratio. To find the amount of each component gas in the 

 larger volume of air at the beginning necessary to make a certain per- 

 centage of nitrogen at the diminished volume, therefore, one has only 

 to multiply the nitrogen ratio mentioned by the per cent of each com- 

 ponent gas present in the gas mixture at the beginning. The difference 

 between the volumes of component gases so found and the per cents 

 (i. e., volumes per 100 c. c.) of the same gases at the end of the ex- 

 periment must equal the actual loss or gain, per 100 c. c. of respired 

 air, of each component gas — du,e to its absorption or excretion by the 

 insect. 



80.61 



Thus in the experiment recorded above, the nitrogen ratio would be ; 



79.24 

 and for 100 c. c. of the respired air, the larger ^-olume of that air at the beginning 

 contained: 



80.61 



C0o= 0.05 X = 0.05 CO. 



79.24 

 80.61 



0„ = 20 . 69 X = 21 . 04 c. c. 



79.24 

 COo excreted per 100 c. c. of respired air = 3.14—0.05 = 3.09 c. c. (gain in COj). 

 The On absorbed per 100 c. c. of respired air = 21.04—16.24 = 4.8 (loss in 00- 



COo 3.09 



Respiratory quotient = = = 0.64. 



O2 4.80 



Table IV gives the results of some respiration experiments carried 

 out by the method just described with a few species of insects in air. 

 Moist air at temperatures between 20° and 24° C. was used. 



