CHANGES DURING PREGNANCY 553 



figures per kilo per hour which he obtained were 462 c.c. C0 2 for 

 the mother and 509 c.c. CO 2 for the foetus. The difference 

 between these figures is within the rather high limits of error in 

 such a complicated experiment. He has also shown that the foetal 

 respiratory quotient is unity, indicating that carbohydrates are the 

 source of energy. The same has been found in new-born puppies 

 before suckling (Murlin l ). Russell and Gye - determined the oxygen 

 consumption of embryonic mouse tissue by suspending the minced 

 tissue in blood and analysing the blood in Barcroft's apparatus. 

 They found values much lower than those obtained for normal adult 

 tissues under the same conditions. Their results are therefore more 

 in accord with Pfl tiger's conception. Russell and Woglom 8 in subse- 

 quent observations determined the respiratory quotient of minced 

 embryonic tissue (skin) and found it to be unity. It is well to 

 remember that all these experiments refer only to the foetus in the 

 later stages of development, and that they entirely leave out of 

 account the placental metabolism. In the later stages there is a 

 wide distribution of glycogen throughout the tissues of the fretus, 

 and the foetal liver has assumed its glycogenic function. It is 

 scarcely justifiable to extend Bohr's results to the early stages of 

 pregnancy, when the placenta probably takes a leading part in 

 embryonic development. It may be that at that time also glycogen 

 is the source of energy for the placenta in Rodents, but it cannot 

 be so in Ruminants. In their placentae glycogen is found only in 

 traces, while fat is in considerable amount. Hence we must not assume 

 that in Ruminants the energy is derived from- the combustion of 

 carbohydrates until experimental evidence has been obtained. 



^ith regard to the total energy exchange the older investigations 

 of Oddi and Vicarelli* showed a progressive increase in the con- 

 sumption of oxygen during the last third of pregnancy in rats ; but 

 Magnus-Levy raises the objection that the movements of the animals 

 were not restricted. The observations of Magnus-Levy, 5 F. Miiller, 6 

 and L. Zuntz 7 showed that in the human pregnancy there was 



1 Murlin, "Protein Metabolism in Development," Awr. Jour, of P/tytiol., 

 vol. xxiii., 1908-09. 



2 Russell and Gye, "The Oxygen Consumption of Mouse Tissue," British 

 Jour. Exp. Pal/iol., vol. i., 1920. 



3 Russell and Woglom, "The Respiratory Exchange of Surviving Mouse 

 Tissues, etc.," ibid., vol. i., 1920. 



4 Oddi and Vicarelli, " Influence de la grossesse sur Pechange respiratoire," 

 Arch. ital. de Biol., vol. xv., 1891. 



5 Magnus-Levy, " Stoffwechsel und Nahrungsbedarf in der Schwangerschaft," 

 Vortrag, Zeitsch. f. Oeburtsh. u. <li/iik., vol. Hi., 1904 ; also v. Noorden, loc. rit., 

 vol. i. 



F. Miiller, "Diskussion zum Vortrag von Magnus- Levy," see v. Noorden, 

 loc. cit., vol. i. 



7 Zuntz 'L.), " Der Stoffaustausch zwischen Mutter und Frucht," Ergebn. d. 

 Phys., 1908. ' 

 18 A 



