SECT. II] FAT METABOLISM 1173 



rises to a peak on the 1 8th day of development, and then falls without 

 a break at hatching. This peak corresponds well enough with the 

 peak in the daily increment of fatty acids found by Cahn (Fig. 363), 

 and occurs at the time when the absorption intensity of fatty acids 

 (Fig. 251) is rising away from its 14th day trough, and taking the 

 place of the protein absorption curve, which is descending. It must 

 be admitted, however, that the individual variations in the curve of 

 Vladimirov & Schmidt are considerable, and it would be worth while 

 to repeat their measurements, using perhaps a better method (they 

 employed that of Bang) . 



1 1 -2. Fat Metabolism of Reptilian Eggs 



The fat metabolism of the reptile egg has only once been investi- 

 gated — by Karashima in 1929, who worked with the turtle, Thalasso- 

 chelys corticata. He found a diminution of some 30 per cent., rather 

 low for a terrestrial egg, as the following table shows : 



Karashima also investigated the percentage of free fatty acids, water- 

 soluble and water-insoluble volatile fatty acids, etc., in the egg-fat 

 at the various stages, but these showed no definite changes : the first- 

 named remaining at about 20 per cent, of the total fraction, the 

 second at about 0-9 per cent, and the third at about 0-7 per cent. 

 On the 15th day, however, there was a marked rise in the free fatty 

 acids, no doubt to be interpreted as due to the action of a lipase, since 

 the total fatty acids remained constant. 



11-3. Fat Metabolism of Amphibian Eggs 



The fat metabolism of the developing amphibian egg has been a 

 subject of some difference of opinion between investigators. Parnas 

 & Krasinska measured the total fatty acid content of frog embryos 

 {Rana temporaria) using the Liebermann-Kumagawa-Suto method. 

 As Table 169 shows, they found just as much at the time of hatching 

 as at the beginning of development, and they therefore concluded 

 that none was used as a source of energy. They did, however, find 



