346 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



Table 12 



Distribution of Lipids in Normal Feces of Several Species 

 of Animals in per cent Total Lipids 



Guinea Rab- 

 Category Rat a >& pig c bit c Cat 1 * Dogd Man' 



Type of solvent extraction 



Unsapon. matter 



Total sterol 



Total acids 



Volatile 



Non- volatile 



Solid 



Liquid 



Insol. in light petroleum ether 5 Present 10 — — 10 



« D. C. Edwards and R. P. Cook, Biochem. J., 48, ix (1951). 



b R. O. Thomson, Unpublished observation cited by R. P. Cook," Comparative As- 

 pects of Lipid Absorption and Excretion," in R. T. Williams. Lipid Metabolism, Bio- 

 chem. Soc. Symposia No. 9, Cambridge Univ. Press, 1952, p. 24. 



c R. P. Cook and R. O. Thomson, Quart. J. Exptl. Physiol., 86, 61-74 (1951). 



d W. M. Sperry and W. R. Bloor, J. Biol. Chem., 60, 261-287 (1924). 



e D. C. Edwards and R. P. Cook, Biochem. J., 49, xli (1951). 



/ Ether and ethanol extraction. 



» Ether extraction. 



h Ether extraction after treatment with light petroleum ether. 



fecal fats melted at 43 to 46 °C. 620 According to Hecht, 621 fecal fats usu- 

 ally have melting points 4 to 8°C. higher than those for the food fats. 



In the fatty acid portion of the lipids from dog feces about 30% were 

 solid acids (palmitic and stearic acids, the latter in a slightly higher pro- 

 chiportion) and 60% were liquid acids (largely oleic with possibly some ara- 

 chidonic acid). 599 The balance of the fat fraction (10%) was accounted 

 for as the glycerol moiety. A similar distribution of non-volatile acids 

 is recorded for human feces. 622 



Volatile fatty acids were excreted in a considerable proportion by cats 

 on a coconut oil diet, but only to a slight extent by dogs. 618 However, 

 dogs did excrete volatile fatty acids in definite amounts after a prolonged 

 fat-free diet. The volatile acids were made up of acetic (65%), butyric 

 (23%), and caproic (12%) acids. 599 Cecchini 623 likewise reported that 

 acetic and butyric acids are the main volatile fatty acids in the feces. In 

 the case of human feces, Edwards and Cook 622 reported that the volatile 

 fatty acids comprise 63% of the total lipid. 



620 1. Munk, Arch. path. Anat. u. Physiol. (Virchow's), 122, 302-325 (1890). 



621 A. F. Hecht, Jahrb. Kinderheilk., 62, 613-659 (1905). 



622 D. C. Edwards and R. P. Cook, Biochem. J., 49, xli (1951). 



623 A. Cecchini, Arch, pathol. din. med., 2, 361-392 (1923). 



