12 RESPIRATORY EXCHANGE OF ANIMALS AND MAti 



the whole period of incubation. The respiratory quotient shows that 

 practically the only substance catabolized in this case is fat (R.Q. = 

 071). Though there are occasional discrepancies, especially at first, 

 when the heat production and the respiratory exchange are both very 

 slight, the agreement for the whole period is remarkable. 



In one experiment, covering the period from the eighth to the 

 nineteenth day of incubation, the measured total heat production was 

 1 2 -1 6 cal. and the calculated I2'ii. Fig. I shows the agreement 



too 

 90 

 ao 

 70 



60 

 50 

 40 



so 

 20 



10 



Calr. 



"ound 



8 9 tO // 12 13 /+ /5 16 17 /S /9 



The heat production of the embryo measured directly and indirectly. *JQy& 

 FIG. i. 



obtained in the single determinations. In all the experiments taken 

 together they find a total heat production, from the third to the nine- 

 teenth day, of 12-58 cal. observed by direct calorimetry and I2'2i 

 calculated from the respiratory exchange. This shows that no energy 

 is stored by the synthesis of living tissues from dead protein, and that 

 the indirect calorimetry can, therefore, be safely employed in growing 

 organisms, where such syntheses take place. 



In cases in which the catabolism is incomplete, or in which en- 

 dothermic processes are taking place to a quantitatively appreciable 

 extent, an agreement between the results of direct and indirect calori- 



