1 1 7© 



FAT METABOLISM 



[PT. Ill 



i30r 



120 



Days -*■ 5 



Fig. 364. 



parisons between the behaviour of the true fatty acids and the Hpoids, 

 and his calculations of tissue constants will be discussed more easily 

 in the Section on lipoids and sterols. He also calculated the percentage 

 growth-rate of the fatty acids of the triglycerides, obtaining a curious 

 result which he did not explain. The curves plotted in Fig. 364 are, 

 firstly, the percentage growth-rate (Minot) of the wet weight of the 

 embryo, secondly, a composite curve for the growth-rate of dry weight, 

 calorific value, total carbohy- 

 drate, coagulable protein, and 

 total ether-alcohol extract, all 

 taken from the data of Murray 

 and Needham. The dry weight 

 growth-rate exhibits a plateau 

 between the loth and 15th days 

 because the dry weight is then 

 most rapidly increasing, but 

 Cahn's curve for growth-rate 

 of triglyceride fatty acids has 

 not a plateau, but a peak. On 

 the other hand, his percentage 

 growth-rate curves for lipoid phosphorus and for cholesterol follow 

 approximately the usual course. 



Something must next be said about the variations in the nature of 

 the fatty acids in the egg at the different stages of development. 

 Mottram showed in 191 3 that the mean iodine value of the fatty 

 acids in the hen's egg was constant, and did not vary greatly. He 

 studied the individual variations, and the effect of incubation on in- 

 fertile eggs, and his results have already been discussed in Section i. 

 The first week of incubation, he found, affected the iodine value but 

 little in the fertile egg, but he sometimes got evidence of a slight rise, 

 thus: 



Day Iodine value 



o 81 



4 83 



8 88 



12 80 



16 84 



19 86 



He was inclined to regard his results as demonstrating the possibiUty 

 of desaturation outside the liver cells. More interesting were the 

 experiments of Eaves, who estimated the iodine value of the fatty 



