S20 THE PHYSIOLOGY OF REPRODUCTION 



The extra energy production at the end of pregnancy is therefore 

 proportional to the weight of the offspring to be delivered. The 

 increase over the metabolism of the mother during sexual rest 

 amounted to about ten per cent, in the first pregnancy and to as 

 much as fifty per cent, in the second pregnancy with five puppies. 



In the human subject, where the weight of the fcetus in proportion 

 to that of the mother is much smaller, the energy metabolism 

 expressed per kilogramme and hour is in the last month of pregnancy 

 only four per cent, larger than for a woman in complete sexual rest : 

 0"99 Gal. per kg. and hour in the latter condition, 1-03 Gal. per kg. 

 and hour in the pregnant woman. This quantitative difference must 

 be borne in mind in comparing observations on pregnant dogs with 

 those on human subjects. "Whatever changes occur are likely to be 

 more pronounced and acute in the dog. 



Directly or indirectly the mother must provide the additional 

 energy and food materials necessarj'' for building up and maintaining 

 the developing embryo. Does this entail a sacrifice on the part of 

 the mother ? At first sight one would conclude a priori that this 

 must necessarily be the case. This idea gradually developed into 

 the conception that pregnancy involved a pathological condition of 

 the maternal organism, and a good deal of experimental evidence 

 was adduced in support of the view that in pregnancy the oxidative 

 processes in the organism are essentially different from the normal. 

 This view found its extreme expression in the dictum of Massen ^ 

 that "a pregnant woman is by the diminished oxidation brought 

 into a condition of auto4ntoxication very similar to that produced' 

 in an animal with an Eck's fistula," where the blood flows from the 

 portal vein directly into the vena cava, without passing through 

 the liver. Similarly, Ewing ^ speaks of a " liver of pregnancy " and 

 holds that normal pregnancy produces changes, especially in the 

 liver, " difficult to separate from the pathological." 



But more recent observations, especially the magnificent work of 

 Bar^ and his collaborators, which has been confirmed in its main 

 results and extended by the careful investigations of Hoffstrom * and 

 Murhn,^ have shown that in a normal pregnancy the maternal 

 organism is very far from being in a pathological condition, and that 



1 Massen, Froc. Soc. for Obstetrics and Oynmcology of St. Petersburg, Feb. 

 1899 ; Zeitsck. f. OebwtshUlfe, vol. x. ; quoted from Bar, see below. 



2 Ewing, "The Pathogenesis of the Toxsemia of Pregnancy," Amer. Jour, 

 of Medical Sciences, vol. cxxxix., "1910. 



^ Paul Bar, loc. cit. 



* Hoffstrom, loc. cit. 



^ Murlin, "The Metabolism of Development," I., II., and III., Amer. Jour, 

 of Physiol., vol. xxvi., 1910 ; vol. xxvii., 1910 ; vol. xxviii., 1911. A summary 

 of these papers is given in the paper by Murlin, "The Nutrition of the 

 Embryo," Trans. \bth Internat. iimgress of Hygiene, September 1912. 



