io6 RESPIRATORY EXCHANGE OE ANIMALS AND MAN 



respiratory exchange methods must therefore be regarded as valid and 

 we may proceed to discuss the results of such investigations. 



Warburg [1908, 1909] measured the respiratory exchange (oxygen 

 absorption) of the eggs of sea urchins (Arbacid]. He found that a very 

 large increase in metabolism took place as the result of fertilization. 

 One hundred and seventeen million eggs, containing I gr. of nitrogen, 

 consumed per hour before fertilization 2*0 mg. of oxygen, after fertiliza- 

 tion 13*6 mg. It would be natural to assume that this increase de- 

 pends upon the functional activity, the process of mitosis and 

 segmentation which is induced by the fertilization. Warburg's experi- 

 ments show very clearly, however, that such a dependence does not 

 exist. A corresponding or even greater increase in metabolism can be 

 brought about in the unfertilized eggs by a number of substances (see 

 p. 67), and after fertilization the segmentation can be inhibited, e.g. 

 by phenylurethane, while the oxygen absorption is not affected at all. 

 On the other hand we cannot have segmentation except when the re- 

 spiratory exchange is increased either by fertilization or as the effect of 

 some chemical agency. In his latest publication [1914] Warburg 

 has shown that the increase in oxygen absorption following immedi- 

 ately upon fertilization is due to the alteration of the surface layer 

 (" Grenzschicht ") of the protoplasm. 



When the eggs develop in normal sea water after normal fertilization 

 the amount of oxygen absorption necessary to reach a certain stage 

 is constant (at least at a constant temperature 1 ), but if the eggs have 

 each been fertilized by more than one spermatozoon, the velocity of 

 segmentation is increased without a corresponding increase in meta- 

 bolism, and the stage of 4 cells may be reached with about one-half 

 the normal oxygen absorption. 



As segmentation progresses the respiratory exchange is increased. 

 In one experiment Warburg found for instance an oxygen absorption 

 of 13*2 mg. per gr. nitrogen per hour at the stage of 8 cells and in 

 the stage of 32 cells 20-5 mg. 



Meyerhof [1911] determined directly the heat production in the 

 different stages and found at 19 the data in Table XIX. 



Meyerhof s figures for oxygen absorption agree on the whole with 

 those obtained by Warburg. 



Meyerhof determined also the heat production of the spermatozoa 

 and found per gr. nitrogen, when the spermatozoa were quite fresh, 

 880 calories per hour. The heat production decreased rapidly. 



1 All Warburg's experiments were made at a temperature of 20-2 to 20-5 C. 



