66o 



THE RESPIRATION AND 



[PT. Ill 



The respiration of nematode eggs has also been studied by Faure- 

 Fremiet, who employed Ascaris megalocephala as material, and the 

 old-fashioned Bonnier-Mangin apparatus as technique. Fig. 121 

 shows the curves he obtained for oxygen intake and carbon dioxide 

 output. These are for i gm. of dry weight, and so are true metabolic 

 rate curves. They differ very much for those obtained on all other 

 animals, for, instead of rising as development proceeds, as occurs 

 both as regards respiratory rate and total amount respired in all 

 other cases, they maintain a practically uniform level. Their absolute 

 value approaches that of some fragmentary figures later given by 

 Holthusen. One gram dry weight of vermiform embryos ready to 

 hatch thus consume no more oxygen in 24 hours than one gram 

 20 



24 



48 



72 



Hours 



Fig. 121, 



of dry weight of newly fertilised eggs, a strange state of affairs, which 

 may be related to the fact that, in later life, Ascaris differs from all 

 the other examples in being eventually anaerobic. During develop- 

 ment, Faure-Fremiet found that 50 c.c. of oxygen were absorbed 

 and 43-8 c.c. of carbon dioxide given out per gram dry weight, and 

 this led to some interesting calculations concerning the general 

 metaboUsm, for which see later. The respiratory quotient for the 

 whole period was 0-876, but, when it was calculated for each day 

 during the 120 hours of development, the graph shown in Fig. 122 

 was obtained. During the earlier stages of development, the respira- 

 tory quotient fell from 0-82 at the 24th hour to reach 0-74 at the 

 72nd hour, after which it rose steadily, though more rapidly at 

 first than later, to 0-92 at the end of development. It was therefore 

 declining during the stages of segmentation and gastrulation, it 



