588 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



was confined to the outermost layer of the outer back fat, and was not 

 noted in the inner layer. Thus, the iodine number of five samples of sow 

 back fat representing layers progressively deeper below the surface were 

 70.4, 67.4, 62.9, 63.0, and 62.8. In the deeper samples, some increase was 

 noted in the proportion of the saturated C ]6 and Ci 8 acids, while a definite 

 decrease obtained in the oleic and linoleic acid content, as well as in the 

 unsaturated C20-C22 acids. 



On the other hand, the fats laid down in the several fat depots of the rat 

 were shown by Reed et al. 2b0 to have similar iodine numbers. The dif- 

 ferences found between the samples from the diverse fat depots were less 

 than the variations between the fats from any one depot obtained from 

 different rats within the same group. The similarity in deposit fat in dif- 

 ferent locations likewise applies for the dog and for the duck. 



Although the temperature of the tissues may to some extent be associated 

 with the hardness of the fat deposited, this is not invariably the case. Such 

 warm-blooded marine animals as the Indian dugong or sea-cow (Halicore 

 dugong), which has a body temperature of 102° to 104°F., and the porpoise 

 (Phocaena spp.), 297 with a body temperature of 96° to 98.6°F., have fats 

 similar to those of the cold-blooded fishes; the same series of highly un- 

 saturated acids are present in both types of marine life. Although it is 

 evident that body temperature may play some part in determining the 

 nature of deposit fat, it is obviously a less important factor than is species 

 or the type of food fat ingested. 



(b) The Effect on Vegetable Fats. It is well known that the composition 

 of vegetable oils may, to some extent, be related to the environmental con- 

 ditions under which they are produced. The most important factor in 

 determining the composition of such fats is temperature. Ivanov 297 ~ 302 

 and Juschkevitsch 303 are of the opinion that fats having a larger proportion 



297 S. Ivanov, Bull. Appl. Bot. and Plant Breed. (Leningrad), 13, No. 2, 483-491 

 (1922-1923); Chem. AbsL, 20, 2349 (1926). 



298 S. Ivanov, Fortschr. Naturwiss.-Forsch. (Abderhalden's) n.s., 5, 1-39 (1929). 



299 S. Ivanov, Ber. dent. Botan. Ges., 44, 31-39 (1926); also cited by T. P. Hilditch, 

 The Chemical Constitution of Natural Fats, 2nd ed., Wiley, New York, 1947, p. 162. 



300 S. Ivanov, Z. angew. Chem,, 42, 292 (1929). 



301 S. Ivanov, Chem. Umschau Gebiete Fette, die, Wachse, u. Harze, 38, 96-100 (1931); 

 cited by T. P. Hilditch, The Chemical Constitution of Natural Fats, 2nd ed., Wiley, New 

 York, i947, p. 162. 



302 S. Ivanov, Allgem. Oel-Fett-Ztg., 29, 149-150 (1942); Chem. AbsL, 27, 2053-2054 

 (1933); cited by T. P. Hilditch, The Chemical Constitution of Natural Fats, 2nd ed., p. 

 162. 



303 S. Juschkevitsch, Fettchem. Umschau, 40, 197-200 (1933); Chem. AbsL, 28, 355 

 (1934); cited by T. P. Hilditch, The Chemical Constitution of Natural Fats, 2nd ed., p. 

 162. 



