LIPID CONTENT AND COMPOSITION OF ANIMAL 587 



Henriques and Hansen 18 reported that fat from the back of the pig has a 

 melting point related to the environmental temperature. In one pig, kept 

 in a room at 30 to 35 °C. for two months, the iodine number of the fat was 

 69.4. In a litter-mate kept on the same diet at an environmental tem- 

 perature of 0°C, the iodine value of the back fat was 72.3 while, in a third 

 pig from the same litter, which was also maintained at 0°C. but which was 

 protected by a fur coat, the iodine value of the fat was only 67.0. Thus, it 

 was suggested that a low environmental temperature tends to result in the 

 production of a low-melting fat (high iodine number), while more elevated 

 outside temperatures cause the production of higher-melting fats having 

 lower degrees of unsaturation. 



Variations in the melting point of a fat may be related to the site at which 

 it is deposited in the body. In birds, where the skin is well protected from 

 the effect of external temperature, the depot fats have a fairly uniform com- 

 position, irrespective of whether they represent samples from internal or- 

 gans or from superficial tissues. On the other hand, in the pig, which does 

 not possess an external covering, corresponding to feathers, for protection 

 from cold, the perinephric fat has the highest melting point, while that 

 from the outermost back fat has the lowest melting point. The differences 

 in melting point and iodine value for fats obtained from different sites in 

 the pig are shown in Table 14. 



Table 14 



A Comparison of the Solidifying Point and Iodine Values of Fat 



with the Temperature of the Tissues of the Pig" 



Body 

 Solidifying Iodine Site for detn. of temp., 



Source of body fat pt., °C. value body temp. °C. 



Outer layer of back fat Back tissue 



1st layer — 60.0 1 cm. deep 33.7 



2nd layer (inner) 26.4 57.1 2 cm. deep 34.8 



Inner layer of back fat 



3rd layer 28.0 51.8 3 cm. deep 37.0 



4th layer 27.7 50.6 4 cm. deep 39.0 



Perinephric fat 29.6 47.7 Rectum 39.9 



a V. Henriques and C. Hansen, Skand. Arch. Physiol, 11, 151-165 (1901), pp. 155, 161. 



The results of Henriques and Hansen 18 are in agreement with those of 

 Lummert, 20 and have been confirmed by Schirmer 296 and by Dean and 

 Hilditch. 80 However, the latter workers reported that the unsaturation 



296 O. Schirmer, Arch, exptl. Pathol, u. Pharmakol. (Naunyn-Schmiedeberg's), 89, 263- 

 279(1921). 



