426 ORIGIN OF MILK FAT 



from which the oil had been removed) showed that in this 

 period the animal produced in her milk about fifty pounds 

 more fat than she consumed with her food. And yet the 

 cow had become much fatter; the actual amount of newly 

 formed fat must, therefore, have been much more than this. 

 The extent of protein decomposition, determined by the 

 nitrogen output, was at the same time far from being suf- 

 ficient to explain in any degree the new formation of fat. 

 The bulk of the latter was certainly derived, therefore, from 

 the carbohydrates of the food. 76 



Lower Fatty Acids in Milk. Besides the typical higher 

 fatty acids (palmitic, stearic and oleic acid) there are also 

 small quantities of the lower fatty acids in milk, the presence 

 of which is the more interesting because it offers a very im- 

 portant and, as far as the author knows, hitherto little con- 

 sidered suggestion as to the nature and the method actually 

 followed by physiological catabolism of the higher fatty acids 

 in the economy. It is certainly not a matter of accident that 

 only normal fatty acids with unbranched chains and an even 

 number of carbon atoms are to be found along with the 

 higher fatty acids in milk, namely, myristic acid, C 14 ; lauric 

 acid, C 12 ; capric acid, C 10 ; caprylic acid, C 8 ; caproic acid, 

 C 6 , and butyric acid, C 4 . 77 Elsewhere, too, we find precisely 

 these same normal fatty acids with paired carbon atoms 

 (considering here the acids with more than three carbon 

 atoms) emerging in all sorts of places from the sea of 

 metabolism. That we once ina while meet withisobutyric acid, 



>CH COOH, and isovalerianic acid. "NcH CH 2 COOH, 



CH/ 



is not of any special moment, because these may be regarded 



78 W. Jordan and C. G. Jenter, New York Agric. Exp. Station Bulletin, 1897. 

 77 The only seeming exception to this rule known to the author, a statement 



of Chevreul as to the occurrence of isobutylacetic acid, J>CH CH 2 



CH 2 COOH, and of isovalerianic acid in cow's butter, may not be held as 

 of very great importance when we remember the great age of the observation, 

 almost a century. Cf. W. R. Raudnitz, 1. c., p. 260. 



