384 FAT METABOLISM. OBESITY 



within the egg, the fact has been noted that the former 

 gradually grows poor in unsaturated acids, corresponding 

 with the greater mobility and resorption of oleic acid (in 

 contrast to stearic and palmitic acids). On the other hand, 

 the gradual increase in the iodine value of the organized fat 

 of the embryo chick indicate that saturated acids in the 

 embryo are undergoing conversion into unsaturated acids 

 (v. inf.). 13 



Depot Fat and Cell Fat. According to studies of Abder- 

 halden and Brahm it would be well in the study of fat 

 metabolism to distinguish between depot-fat and cell-fat. 

 In order to determine whether not only the former but also 

 the fat directly involved in the construction of the body cells 

 is dependent upon the character of the food fat ingested, 

 dogs were fed for a long time with mutton suet or with 

 rape-seed oil and then killed. The readily extracted depot-fat 

 is then removed by ether. In order to make it possible to 

 extract the cell-fat, however, the tissue to be subjected to 

 ether is digested or broken up by dilute hydrochloric acid. 

 It is interesting to note from this procedure that the proper 

 cell-fat in contrast to the depot-fat is independent of the 

 character of the ingested food. 14 



This difference between depot-fat and cell-fat acquires 

 special significance when it is recognized that a considerable 

 fraction of the ethereal extract from the liver, heart, kidneys 

 and other tissues does not consist of ordinary neutral fat 

 but of phosphatides of many types (v. Vol. I of this series, 

 pp. 171-172, Chemistry of the Tissues), which contain be- 

 sides the typical high fatty acids even a higher proportion 

 of unsaturated fatty acids of the linseed oil and linolic acid 

 series. 15 There is perhaps some connection between the fact 



13 E. C. Eaves ( Instit. of Physiol., Univ. College, London ) , Jour, of Physiol., 

 40, No. 6, 1910. 



14 E. Abderhalden and C. Brahm, Zeitschr. f. physiol. Chem., 65, 330, 1909. 

 '"Rubow, Heffter, Henriques and Hansen, Erlandsen, Hartley, Leathes 



and Kennaway and others. Literature: J. B. Leathes, Ergebn. d. Physiol., 

 8, 366-370, 1909. 



