CHANGES IN THE MATERNAL ORGANISM 513 



strated laurinic acid in considerable amount in the foetuses. 

 Hence the fat of the food, or at least one of its fatty acids, 

 had been transmitted across the placenta. But any conclusions 

 based on the introduction of a foreign fat must be guarded. 



In the foetus, fat is present in many of the tissues in a stale " 

 of fine division. Its wide-spread distribution and its amount, 

 probably equal at least to that of glycogen, are a characteristic 

 of foetal life ; but its significance is not obvious if, as Bohr 

 states, it is not a source of energy. Guillot l showed that it did 

 become a source of energy immediately after birth. He found 

 12 per cent, of fat in the lungs of foetuses dying during labour, 

 and only 6 per cent, after several hours* respiration. Fat may 

 have anabolic functions to perform in the building up of the 

 foetal body, e.g. in the synthesis of lecithin. 



e. The Excretion of Fat Derivatives in Pregnancy. The 

 primary product is oxybutyric acid. This, by oxidation, is 

 transformed to aceto-acetic acid, which in turn gives rise to 

 acetone by the loss of carbon dioxide from the molecule. Little 

 is known regarding the excretion of aceto-acetic acid and oxy- 

 butyric acid in apparently normal pregnancies, though in patho- 

 logical cases of persistent vomiting, with a high degree of inanition, 

 the latter may often appear (Kraus 2 ). This is to be expected. 

 In general, if the amount of oxybutyric acid is small, acetone 

 alone appears in the urine ; if in greater amount diacetic acid 

 may also be present, and, if greater still, all three maybe excreted. 3 



That acetonuria exists in pregnancy is certain, but in the 

 majority of cases it does not pass the physiological limit 

 (Stolz 4 ). If it is in greater abundance, some special factor must 

 be at work, It is not enough to say that its presence is always 

 due to the exclusion of carbohydrates in varying degrees from 

 the metabolism, 5 leading to a lowered oxidation of fats by the 



1 Guillot, quoted in Richet's Dictionnaire de Physiologic, Article " Foetus." 



2 Kraus, quoted in v. Winckel's Handbuch der Oeburtshulfe, vol. i., H. 1. 



3 See v. Noorden, loc. cit., vol. i. 



4 Stolz, "Die Acetonurie in der Schwangerschaft," Arch. f. Gyndk., 

 vol. Ixv. 



5 Wolfe ("The Chemistry of Toxaemias in Pregnancy," New York Med. 

 Journ., 1906) states that there is no connection between acetone compounds 

 in the urine and the essential features of hyperemesis gravidarum', a condi- 

 tion in which there is pre-eminently a deficient absorption of carbohydrates. 



2K 



