7o8 



THE RESPIRATION AND 



[PT. Ill 



the trough in it the conclusion might be drawn that a point of maxi- 

 mum efficiency was passed through at the gth day. But it must be 

 remembered that this curve is the resuk of many contributing sets of 

 figures, and depends on various assumptions which will be discussed 

 later. 



O Q) 



o s» 



14 15 16 17 18 19 20 21 22 

 Day of Incubation 



Fig. 14! 



II m IV V VI vnvm ix x 



Day after hatching 



4-13. Later Work on the Chick's Respiratory Exchange 



Lussana's paper was not devoted solely to the respiration of the 

 chick in the egg. His experiments did not begin till the 14th day 

 of development, but their special interest is that he carried them 

 through the hatching process and for some days afterwards. Fig. 148 

 taken from his paper shows his results for metabolic rate. Beginning 

 at a more or less constant level, just as had been found by the 

 Danish workers, it rose very sharply indeed at hatching, and re- 



