526 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



30 to 40% of its original body weight. The animals were then fed rations 

 high in specific fats until they had regained their original body weight. 

 In the case of one dog which was fed linseed oil, the resulting body fat would 

 not solidify at 0°C, although dog fat normally melts at between 30 and 

 42 °C. In the case of the second dog, which received mutton fat, the de- 

 posited fat melted above 50°C. and yielded a fat "which was almost 

 identical with mutton tallow." Munk 17 performed a similar experiment in 

 which the dietary fat consisted of a high proportion of rapeseed oil. This 

 investigator was able to isolate from the dog fat considerable quantities of 

 erucic acid, which is the principal fatty acid in rapeseed oil, and which is 

 ordinarily absent from animal fat; he correctly postulated that the glyc- 

 eride of the food fat had been deposited in the tissues. 



The above experiments, which may be classed as the extreme type, 

 illustrate the profound effect which dietary fat may exert upon the com- 

 position of storage fat. However, more recent work proves that a similar 

 replacement of normal body fat by specific food fats may occur without 

 the drastic procedure of first removing most of the animal fat by a pro- 

 longed fast period. The more recent data show that a gradual substitution 

 of the new fat occurs if a specific type of diet is continued over a rather 

 extended period. 



a. The Effect of Dietary Fats Containing Short-Chain Acids on the 

 Composition of Storage Fat. A number of workers 18-22 have reported that 

 when such fats as butter and coconut oil, which have a considerable content 

 of relatively short-chain acids, are fed to animals, the iodine value of the 

 depot fat is somewhat reduced. Although this change might indicate that 

 a deposition of saturated short-chain acids was taking place in the storage 

 fat, neither Leube 23 nor Zuntz, 24 who fed butter fat, nor Lebedeff, 28 who 

 fed tributyrin, could detect any increase in the volatile fatty acids in depot 

 fat. Eckstein, 26 using rats, and Davis, 27 experimenting with chickens, 

 have reinforced our evidence that the butyryl radical (C 4 ) cannot be de- 



17 1. Munk, Arch, pathol. Anat. u. Physiol. (Virchow's), 95, 407-467 (1884). 



18 V. Henriques and C. Hansen, Skand. Arch. Phxjsiol., 11, 151-165 (1901). 



19 V. Henriques and C. Hansen, Oversigt kgl. Danske Videnskab. Selskabs Forh., 1899, 

 No. 4, 333-372. 



20 W. Lummert, Arch. ges. Physiol. (Pfliiger's), 71, 176-208 (1898). 



21 J. Konig and J. Schluckebier, Z. Untersuch. Nahr. u. Genussm., 15, 641-661 (1908). 



22 H. D. Gibbs and A. Agcaoili, Philippine J. Sci., 5, Sect. A, 33-43 (1910). 



2 3 W. Leube, Verhandl. Kongr. inn. Med., 18, 418-432 (1895). 



24 N. Zuntz, Z. Untersuch. Nahr. u. Genussm., 4, 126-127 (1901). 



25 A. Lebedeff, Z. physiol. Chem., 6, 139-154 (1882). 



26 H. C. Eckstein, J. Biol. Chem., 81, 613-628 (1929). 



27 R. E. Davis, J. Biol. Chem., 88, 67-75 (1930). 



