FCETAL NUTRITION: THE PLACENTA 465 



which is evidenced by the respiratory exchange, the energy arises 

 from carbohydrates. He arrived at this conclusion as a result of 

 deterfnining the respiratory quotient ^ ill pregnant rabbits and guinea- 

 pigs before and during the compression of the umbilical cord, the 

 difference representing the respiratory exchange in the embryo. 

 He found that the quotient in such cases was unity, thus showing 

 that the substance oxidised in the developing embryo must have 

 been a carbohydrate. Bohr supposed that the energy liberated by 

 the combustions, which in the adult is dissipated largely under the 

 form of heat radiated and water evaporated from the surface of 

 the body, is in the fQ3tus used for the increase and maintenance of 

 the newly formed tissues ; in other words, " the reactions of synthesis, 

 which are so numerous during development, are endothermic or 

 heat-absorbing, and they borrow the heat from other simultaneous 

 exothermic actions," ^ in this case the oxidation of carbohydrates. 



Ferments and Vital Staining 



Frank ^ has carried out an investigation to determine whether 

 any differences existed in the ferment content of the functionating 

 as compared with that of the non-functionating placenta. His 

 results were mostly negative, no definite evidence being afforded 

 either for or against the view that the placenta acts as an accessory 

 organ of metabolism to the foetus. The experiments were mainly 

 upon the rabbit.* The ferments investigated were amylase (or 

 starch hydrolysing ferment), lipase (fat splitting), and erepsin 

 (hydrolysing peptone to amino-acids), and their respective contents 

 were determined by appropriate tests. The amylase content was 

 the same or less than that of the maternal blood, the lipase rather 

 more, and the ereptic content considerably more. The foetal blood 

 contained less ferments than the maternal. Neither foetal nor 

 maternal blood showed any changes in ferment strength in relation 

 to the progress of pregnancy. The organs of large foetuses have 

 high ferment values, sometimes higher than those of the corre- 

 sponding organs in the mother. The investigation upon "vital 

 staining," in which the acid, stain "trypanblau" was injected' 



1 The respiratory quotient is the ratio of CO2 discharged to O2 absorbed, 



CO 



that is, the fraction -=-?. For an exclusively carbohydrate food this is unity ; 



for a fat or protein, less than unity. For a discussion of the subject in 

 relation to^fcetal metabolism see Feldman, Principles of Ante-Natal and Post- 

 Natal Child Physiology, London, 1920. See below, p. 504. 



2 See Eichet's Dictionnaire de Physiologie, vol. vi., Article " Foetus.'' 



^ Frank, "An Experimental Study of the Placenta, etc.," Swg., Gyn. and 

 Ohstet., November 1912. 



■• The animals used were six rabbits, three guinea-pigs, two cats, and a 

 bitch. 



