CHANGES DURING PREGNANCY' 543 



ninth month. In guinea-pigs the fcetal Hver contains considerable 

 amounts of fat, especially towards the end of gestation.'^ This excess 

 of fat, which is less saturated than connective tissue fat, disappears 

 during the first two or three days after birth. 



{(1.) Origin of the Fcetal Fut. — As to its origin, Thiemich '^ states 

 that it is not derived from the alunentary fat of the mother, smce 

 after feeding a dog in two successive pregnancies on widely different 

 fats, palmin and linseed oil, he could determine no difference in the 

 constitution of the foetal fat. Oshima ^ comes to the same conclusion 

 from his investigations on the number of ultra-microscopic particles 

 in the blood of cats, rabbits, and guinea-pigs. He states that the 

 number is dependent on the stage of development, and independent 

 of the condition of the mother's blood — for example, when a great 

 increase is produced by rich fat-feeding. Capaldi, on the other hand, 

 states that the percentage of fat is the same in the maternal and 

 foetal blood, at least at the end of pregnancy. Some feeding experi- 

 ments carried out by Hofbauer * agree with this. He administered 

 coco-nut oil, which consists essentially of the triglycerides of laurinic 

 and myristinic acids with a very small quantity of tripalmitin, to 

 three pregnant guinea-pigs, and demonstrated laurinic acid in con- 

 siderable 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 state of 

 line division. Its widespread distribution and its amount, probably 

 equal at least to that of glycogen, are a characteristic of fcetal life ; 

 but its significance is not obvious if, as Bohr states, it is not a source 

 of energy. Guillot ^ showed that it did become a source of energy 

 immediately after birth, when the foetus is faced suddenly with 

 the necessity to maintain its body temperature against a lower 

 external temperature. The rapid disappearance of fat from the 

 foetal liver, observed by Imrie immediately after birth, also suggests 

 such an explanation, although Imrie himself suggests that the fat in 

 the foetal liver is destined for the connective tissue depots. He found 

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

 and only six per cent, after several hours' respiration. Fat may have 



' Imrie and Graham, "The Fat Content of Embryonic Livers," Join: Biol. 

 Chem., vol. xliv., 1920. ^ 



2 Thiemich, "Ueber die Herkunft des fotaleu Fettes," CeiitralhL f. Pkys., 

 vol. xii., 1898. 



^ Oshima, " Ueber das Vorkommen von ultra-mikioseopischen Teilchen ini 

 fotalen Blute," Centralhl. f. Phys., vol. xxi., 1907. 



■* Hofbauer, Biologie der nienschUclien Plazenta, Wien'and Leipzig, 1905. 



" Guillot, quoted in Richet's Bictionnaire de Physiologie, Article " Fa?tus." 



