^94 



FAT METABOLISM 



[PT. Ill 



into pre-natal life, but it may be presumed that the process is 

 continuous. 



An interesting investigation which involved several aspects of em- 

 bryonic fat metaboHsm was made by Imrie & Graham, who esti- 

 mated the amount of fat and its iodine value in the embryonic and 

 maternal Hvers of guinea-pigs during gestation, using Leathes' method. 

 Fatty infiltration of the liver in the non-pregnant animal is known 

 to be due to the entry of tissue fat into the liver, for the iodine 

 value characterises the fat normally present in the liver and in 

 the other tissues, being high in 

 the former and low in the latter. 

 The question which Imrie & 

 Graham set out to solve was ^ 

 whether the embryonic liver | 

 behaved in the same way, or ^ 

 whether it evinced any special ^ 

 physiological characteristics in 

 its reactions to disturbances of 

 fat metaboHsm. "It seemed 

 reasonable to suppose", they 

 said, ' ' that the embryonic tissue | 

 might possess an avidity for 1 

 food material such as fat and ^ 

 that this might evidence itself i» 

 by a greater accumulation of 

 fat in the embryonic than in 

 the maternal liver, if the fat 

 were mobilised experiment- 

 ally." Obviously it was first 

 necessary to estabhsh normal curves for the embryonic liver fat, and this 

 in itself brought some interesting results, as may be seen from the curves 

 plotted in Fig. 370. It was found that during development the guinea- 

 pig embryo accumulates considerable stores of fatty acids in its liver. 

 At first (up to body-weight 30 gm.) the percentage of fatty acids in 

 the embryonic liver does not differ much from that in the maternal 

 liver, but after that point the percentage in the former rises sharply 

 to reach a maximum at about 80 gm. body-weight (roughly 65 days 

 conception age), after which there is no further change until birth. 

 Immediately upon birth, however, the fatty acid percentage drops 



20 30 40 50 60 70 60 90 lOOnO 

 gms. weight, embryos J" 



Fig. 370. 



