732 THE RESPIRATION AND [pt. iii 



Bell, Cunningham, Jowett, Millet & Brooks; and Haselhorst found 

 the volume percentage of oxygen in the bloods to be as follows : 



Maternal arterial ... 

 Maternal venous ... 

 Foetal arterial 

 Foetal venous 



Bell also made some observations on the alkaUne reserve of the two 

 circulations, obtaining results contrary to the earlier ones of Levy- 

 Solal, Weismann-Netter & Dalsace; Williamson; and Losee & Van 

 Slyke. The English workers found more carbon dioxide combining 

 power in the maternal than in the foetal blood, and the French and 

 American workers found the opposite. 



Table 85. 



Carbon dioxide combining power in 

 vol. % (c.c. per lOO c.c.) 



Maternal Foetal 

 Levy-Solal & associates (4 cases) ... ... 30-4 49-5 



48-1 55-9 



37-8 53-6 



42-0 48-2 



Art. Ven. Ait. Ven. 



Bell & associates (5 cases), average ... 40-45 43*45 37'7 40"0 



Losee & Van Slyke (4 cases), average ... 50-0 53-0 



Williamson (7 cases), average 31-2 34-0 



Rielander ... ... ... ... ... — 37'i 



The role of the placenta in foetal respiration has also been studied 

 by Schmidtt, who in a series of papers has put forward the sug- 

 gestion that the foetal respiratory centre is situated, for a time at 

 least, in the placenta, and not in the embryonic medulla. By per- 

 fusing the placenta with various solutions, and by studying the effect 

 of altering the pH of the perfusing fluid, he found that the acid side 

 would cause vaso-dilation and the alkaline side vaso-constriction, so 

 that a regulatory mechanism of some sort was evidently present^. 



4-16. Heat-production of Mammalian Embryos 



We may now return to the heat-production of the mammalian 

 foetus. Unfortunately this has never been measured directly, for the 

 technical difficulties in doing so have so far been insuperable, and 

 all that we know about it is derived from experiments in which the 



^ There are, of course, no nerves in the mammalian placenta (Ikeda). 



