636 



THE RESPIRATION AND 



[PT. Ill 



cmm. 

 O2 or CO2 



Warburg did not draw any conclusion from this finding, but it 

 has acquired importance in view of subsequent researches on the 

 nature of the substances combusted as energy sources during em- 

 bryonic development. It will be again referred to in the section 

 on the energy relations of the growing 

 embryo. 



The figures given above demon- 

 strated that weight for weight the 

 spermatozoon was respiring more 

 intensely than the egg-cell. When, 

 however, the relations between the 

 respiration of one spermatozoon and 

 one egg-cell were compared, it was 

 found that spermatozoon : unfertilised 

 egg was as i : 500, while spermato- 

 zoon : fertilised egg was as i : 3500. 

 Another interesting calculation which 

 Warburg made from his experimental 

 data was that only 0-0045 mgm. of 

 spermatozoon nitrogen were required 

 to fertilise 7 to 8 mgm. of egg nitrogen, 

 i.e. to fertilise i mgm. of egg nitrogen 

 TsW to 20W mgm. spermatozoon nitro- 

 gen were necessary. One conclusion 

 from all this was that, as far as respira- 

 tion experiments were concerned, it 

 was unnecessary to make much cor- 

 rection for the spermatozoal respira- 

 tion, owing to its extreme smallness. 



The next step forward was taken 

 by Shearer, who in 1922, by using a 

 special form of the Barcroft differential 

 manometer, was able to carry out the 

 fertilisation of Echinus microtuberculatus 

 eggs actually inside the closed chamber of the apparatus, and observe 

 more intimately still the earliest stages of the embryonic respiration. 



Fig. 109, taken from Shearer's paper, shows the phenomena which 

 may under such conditions be observed during the first 10 minutes, 

 i.e. during the period which elapsed between fertilisation and the 



5 minutes 

 Fig. 109. 



