SECT, ii] FAT METABOLISM 1191 



746 mgm. per cent, as against 314 mgm. per cent, in maternal blood, 

 in both cases nearly all in the plasma. They thought it likely that a 

 synthesis of fat by the placenta must occur, but they could not 

 demonstrate the presence of any lipolytic enzyme in it. The other 

 attempts which have been made to gain knowledge about the lipolytic 

 enzymes of the placenta will be discussed in the section on that 

 organ. More recently Slemons & Stander obtained the following 

 figures for foetal and maternal blood at term in man : 



Average 



milligrams % 



Whole blood Maternal ... 908 



Foetal ... 707 



Plasma Maternal ... 942 



Foetal ... 737 



and concluded that the fatty acids of the embryo were not directly 

 derived from the mother. MurHn & Bailey found the same relation 

 in man at term, though their figures were lower than those of 

 Slemons & Stander. . 



Average 

 milligrams % 

 Whole blood Maternal ... 550 



Foetal ... 266 



Murlin & Bailey believed that an association existed between fat- 

 content of foetal blood and severity of labour. 



Another line of evidence against the passage of fatty acids from 

 maternal organism to embryo arises from the fact that, when fats 

 are earmarked in one way or another, they do not subsequently 

 appear in the fat depots of the foetal tissues. Two principal methods 

 have been used for this purpose, firstly, the marking of fatty acids by 

 stains and dyes, and, secondly, the use of special or highly unsaturated 

 fats which can easily be recognised at the other end. Hofbauer was 

 perhaps the first to utilise these methods, for, in his many-sided study 

 of the metabolism of the placenta in 1905, he fed fats stained in 

 various ways to pregnant animals, and stated that he observed traces 

 of the colour afterwards in the foetal fat. The colour can only have 

 been in traces, for in the hands of subsequent experimentalists the 

 results of this type of experiment have been uniformly negative. Thus 

 Gage & Gage in 1909 fed fat stained with Sudan III to various kinds 

 of pregnant animals, and never observed the slightest indication of a 

 passage through the placenta. The maternal fat depots would be 

 brilliantly pink or red, while those of the embryo would be perfectly 



N E II 76 



