816 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



pholipid is increased. In the case of the Atlantic and Mediterranean 

 loggerhead sea-turtle (Thalassochelys corticata (caretta), Chelonia caouanna) , 

 the total fat content of the egg remains fairly constant during incubation, 

 but the free fatty acids increase markedly in the course of this develop- 

 mental period. 621 On the other hand, Takahashi 622 reported that, al- 

 though an increase in the free choline content took place during incubation, 

 the total choline was decreased by 50% by the end of this period. 



There are conflicting reports as to the change in the cholesterol in the 

 egg during incubation. Kusui 623 reported a decrease in cholesterol until 

 the fourteenth day, after which an increase occurred. This indicates that 

 the embryo develops the capability of synthesizing cholesterol after the 

 fourteenth day. On the other hand, Dam 624 - 625 observed considerable 

 irregularity in the cholesterol content of different eggs. This precluded 

 any statements as to the development of the synthetic capacity on the part 

 of the chick. However, Hanes 626 noted that, on the fourteenth day, 

 cholesterol esters appeared in the liver. It was believed that this occurred 

 concomitantly with the decrease in yolk phospholipid. Although Mueller 627 

 reported that no change in the total cholesterol occurred over the period of 

 incubation, he found that ester cholesterol increased from practically up 

 to the thirteenth day to about 40% of the total at hatching. Several 

 workers have been unable to demonstrate any synthesis of cholesterol 

 during the incubation of the hens' eggs, 628,629 but others produced some ex- 

 perimental evidence of synthesis. 625,630 



The composition of various types of eggs, as reflected by their fat metab- 

 olism, was exhaustively reviewed by Needham 615 in 1931. 



621 J. Karashima, J. Biochem. (Japan), 10, 375-377 (1929). 



622 M. Takahashi, /. Biochem. {Japan), 10, 443-449 (1929). 



623 K. Kusui, Z. physiol. Chem., 181, 101-106 (1929). 



624 H. Dam, Biochem. Z., 194, 188-196 (1928). 

 626 H. Dam, Biochem. Z., 215, 475-492 (1929). 



626 F. M. Hanes, /. Exptl. Med., 16, 512-526 (1912). 



627 J. H. Mueller, /. Biol. Chem., 21, 23-28 (1915). 



628 A. H. Roffo and I. Azaretti, Bol. inst. med. exptl., estud. cancer (Buenos Aires), 8, 

 629-632 (1926). 



629 G. W. Ellis and J. A. Gardner, Proc. Roy. Soc. London, B81, 129-132 (1909). 



630 S. J. Thannhauser and H. Schaber, Z. physiol. Chem., 127, 278-280 (1923). 



