542 THE PHYSIOLOGY OF REPRODUCTION 



which occurs in hunger. This "physiological" infiltration is duo 

 to a mobilisation of fat from the depots. It passes first to the liver 

 where it is desaturated and then passes on to the tissues. 



A very significant change m the metabolism of fats — using the 

 term fat here to include lipoids — ^is the great increase in cholesterin 

 and cholesterinesters in the blood during pregnancy. There is also 

 an increase in the true fats (glycerinesters) but not in the phos- 

 phorised fats (lecithin). This was first recognised by Herrmann and 

 Neumann ^ and has been confirmed by many workers. There is an 

 associated increase in the storage of these substances in the corpora . 

 lutea and in the adrenal cortex. The blood of the foetus contains 

 always less cholesterin than the maternal blood and does not contain 

 ^ny cholesterinesters at all. The hyper-cholesterinremia of the 

 mother diminishes towards the end of pregnancy and with the 

 beginning of lactation : there is an ' outpouring of these substances 

 in the milk. It is found accordingly that the hypercholesterinaemia 

 passes off more qiiickly in mothers who suckle their children than 

 in those who do not. The bile of the mother is also richer in 

 cholesterin, and according to M'Nee ^ this may account for the more 

 frequent occurrence of gaU-stones in women. The function of 

 cholesterin is not definitely known, although there is no lack of 

 speculation concerning it. The meaning of this hypercholesterinsemia 

 of pregnancy is therefore not yet understood. 



In the placenta there is evidence of a transmission of fat to the 

 product of conception. Even in the early stages of pregnancy the cells 

 of the uterine mucosa are infiltrated with fat, and the trophoblast is 

 pervaded with fat globules. In Ungulates a large amount of fat 

 is contained in the uterine milk (see p. 435). In those mammalian 

 orders in which the trophoblast is directly bathed by maternal blood, 

 the fat dissolved in it forms a second available supply: There is no 

 reason to doubt an active transference of fat from the mother, or 

 to assume that a transformation from carbohydrates or proteins is 

 necessary. 



(c.) Tfie Daily Bequirertient of Fat for the Foetus. — The daily require- 

 ment of fat varies very considerably during pregnancy, and especially 

 towards the end, when the subcutaneous fat of the foetus is deposited. 

 Febling ^ found 0-5 per cent, of fat in the human foetus at the fourth 

 month, over four per cent, at the eighth, and nine per cent, at the 



' Herrmann and Neumann, " Uber die Lipoide der Graviditat, etc.," Witner I 

 k-lin. Wochenschrift, vol. xxv., 1912. 



^ M'Nee, "Cholesterin: An Account of its Relations to Pathology and 

 Physiology," Quar. Jour. Medicine, vol. vii., 1914. This paper contains a 

 complete bibliography up to 1914. 



^ Fehling, "Beitrage zur Physiologie des placentaren Stoffverkehrs," Arch, 

 f. Gynak., vol. xi., 187T. 



