194 III. CHEMISTRY OF NEUTRAL FATS 



linolenic, and arachidonic acids, respectively. Wagner'^* could not con- 

 firm the presence of linolenic acid, although he did prove that linoleic and 

 arachidonic acids are present. Cramer and Brown ^'^ reported important 

 amounts of tetradecenoic as well as of hexadecenoic acid in all five samples 

 of human fat which they examined. The composition of typical animal 

 fats is included in Table 6, while the results of Cramer and Brown^'* on 

 human fat are included in Table 7. 



Table 7 

 Fatty Acid Content of Human Fat (Weight Per Cent)" 



» D. L. Cramer and J. B. Brown, J. Biol. Chem., 151, 427-438 (1943), p. 428. 



(c) Composition of Milk Fats. The composition of the milk fats shows a 

 certain uniformity in various species. Thus, the myristic and palmitic 

 acids are in fair agreement in samples from mature animals of a number of 

 species, being 7-12% and 23-31%, respectively. Oleic acid, also, shows 

 considerable uniformity, varying only from 28 to 41% in all types re- 

 ported. 



However, there are a number of important differences between human 

 milk fat and that from the lower animals. The chief one is the extremely 

 low content of butyric, caproic, and caprylic acids in human milk in con- 

 trast to their relatively high proportion in goat and cow milk. Human 

 milk also contains a larger proportion of octadecadienoic acid than is found 

 in any other milk fats examined, but this might be attributable to diet. 

 The presence of Cio-w unsaturated fatty acids in milk fat from the cow, 

 goat, and human subject seems to be slight but definite. The function of 

 these monoethenoid acids is unknown. Achaya and Banerjee^^^ recently 

 reported a maximum of 15.4% of butyric acid in the milk fat of the Indian 

 buffalo. This represents by far the highest concentration of this acid 

 found in natural fats. The composition of milk fats from several varieties 

 of animals is included in Table 8. 



"8 O. Wagner, Biochem. Z., 174, 412^19 (1926). 



"« K. T. Achaya and B. N. Banerjee, Biochem. J., 40, 664-669 (1946). 



