734 



THE RESPIRATION AND 



[PT. Ill 



remained perfectly constant during pregnancy, there was a possibility 

 of determining how the foetal metabolic rate varied. Murlin also 

 estimated the heat-production throughout pregnancy, and a curve 

 plotted from his figures is shown in Fig. 162. No appreciable increase 

 occurred until gestation had been half accomplished. Murlin calcu- 

 lated that the extra metabolism due to the embryo (and all accessory 

 structures) at the end of pregnancy was almost exactly equivalent to 

 the amount which a newly born animal of the same weight would 

 theoretically produce (according to Rubner's skin-area law) if exposed 

 to ordinary room temperature 

 and resting. Thus in the case 

 of the I -puppy pregnancy, the 

 extra metabolism was 46-0 cal., 

 and the extra metabolism cal- 

 culated by Meeh's formula from 

 the embryo-weight was 45-4. 

 Similarly the extra metabolism 

 in the case of the 5-puppy preg- 

 nancy was 258-5, and the same 

 calculated from the embryo- 

 weights was 251-6 gm. cal. Thus the total curve for mother and 

 offspring should not suffer any change at birth, if all muscular 

 movement were abolished. Murlin & Carpenter were later able to 

 verify this in the case of man where there was no muscular movement. 



The estimations of L. Zuntz; Murlin & Carpenter and Hasselbalch 

 all agreed in showing an extra basal metabolism near term of about 

 4 per cent. Apart from this small increase the heat given off per 

 unit weight per unit time, according to Murlin, was the same as 

 under normal conditions, i.e. the embryo functions as so much 

 maternal tissue, its higher metabolic rate being just counterbalanced 

 by the inactive and relatively inactive structures. Another exact 

 compensation was that the increase in oxidation of the infant's body 

 when it passes from the warm environment of the uterus to the cold 

 of the outside world was almost exactly equivalent to the oxidation 

 rate of the accessory structures that supported it in utero. 



Other researches on the basal metabolism during pregnancy in man 

 are those of Baer; Cornell; Wilson & Bourne; Haselhorst & Plant; 

 Root & Root ; Sandiford & Wheeler and Rowe, Alcott & Mortimer. 

 The first two of these sets of data are believed by Harding to be faulty, 



Weeks of pregnancy 

 Fig. 162. 



