SECT. 5] IN ONTOGENESIS 819 



be about 24 mgm., or 1-2 mgm. per egg per day. Infertile eggs 

 show, therefore, the following effects within 20 days after laying: 



Loss of 0-2 mgm. carbon dioxide per egg per day (Smith). 

 Loss of 0-072 cal. per egg per day (Langworthy & Barott). 

 Loss of I -2 mgm. glucose per egg per day (Pucher) . 



Smith's figure requires comment in view of the fact that eggs after 

 leaving the hen, give off carbon dioxide to the environment, which 

 is less saturated with that gas than the maternal body. Earlier work 

 by Stepanek and by Atwood & Weakley (see Fig, 152), had resulted 

 in values of the order of 10 mgms. of CO2 per egg per day, but these 

 were for the first week after laying. Smith's figure for the same 

 period was about 3 mgms., but calculation shows that even this 

 amount cannot be accounted for on the view that the egg is giving 

 off the CO2 which has been physically dissolved in it. It is necessary 

 to postulate some acid in the shell liberating carbon dioxide from 

 the carbonates there. 



A steady level of 0-2 mgms. per egg per day, then, is reached by 

 about a month after laying. The heat produced with this would be 

 of the order of 0-37 cal., which would be more than ample to provide 

 {a) for the heat output found by Langworthy & Barott, and (b) for 

 the "Konzentrationsarbeit" of Straub & Hoogerduyn. The latter 

 authors showed that their heat requirement could be satisfied by the 

 daily combustion of 0-0025 mgm. of glucose. They also gave a theo- 

 retical excursus suggesting physical mechanisms by means of which 

 this energy could be used at the membrane surface in the way they 

 postulated. They regarded the vitelline membrane as a "galvanic 

 combustion-element" for glucose with oxygen to carbon dioxide and 

 water, so that the maintenance of specific concentration difference 

 between the exterior and the interior would be a complicated case of 

 concentration polarisation^. (For the histology of the membrane see 

 Lecaillon.) 



The egg of the pigeon (Riddle & Reinhart) and that of the mackerel 

 (Alsterberg & Hakansson) show a very strong positive Manoilov 

 reaction, which is probably to be interpreted as indicating a very 

 weak metabolic intensity in the ovum before fertilisation. 



1 It was later shown by Hill, however, that infertile eggs kept in pure hydrogen for 

 a month still retained the normal difference in osmotic pressure between their yolk and 

 white. Whatever the mechanism of osmotic work may be, it can function anaerobically. 

 In this connection the glycolytic power of the yolk, studied by Stepanek and by Tomita, 

 should be remembered (see Sections 8-13 and 14-6). 



