208 W. R. BLOOR 



temporary accumulations of fat occur and is the most important gland i 

 the organism the probable correctness of Leathes' hypothesis as regards 

 desaturation must be admitted. That phosphorization takes place in othi 

 locations than the liver is indicated by work on changes in fat in th 

 blood in which it is shown that the blood cells may have this functioi 

 Allowing the correctness of the assumption that phospholipoid ("lecithin" 

 is the essential intermediate step in fat metabolism, the questions of f; 

 transport in the blood and in and out across cell walls after it enters tb 

 blood stream as well as its further utilization are greatly simplified, sin 

 lecithin is soluble in the blood plasma and since there are present in a 

 organs and tissues esterases which hydrolyze lecithin readily but whii 

 have little effect on the fats. That blood lecithin may be a source of fa 

 in the living organism is well shown by the work of Meigs and coworke: 

 who found that milk fat could be satisfactorily accounted for by decreas 

 in lecithin in the blood passing through the mammary gland. 



Later Stages (3-oxidation. As regards later stages in the inte: 

 mediary metabolism of the fats little is definitely known. The fatty aci 

 ordinarily disappear in metabolism without leaving any traces in the wa 

 of intermediate stages by which the process of breakdown may be f ollowi 

 In certain cases, however, as in severe diabetes and even in short peri 

 of fasting, acids appear in the urine which are now believed to be late 

 stages of fatty acid combustion. These unburned residues are P-ox 

 butyric and diacetic acids which with their derivative acetone constitu 

 the "acetone bodies." That these substances are actually stages in th 

 breakdown of the fatty acids is strongly indicated by the work of Knoo 

 whose hypothesis of (3-oxidation seems to account satisfactorily for tb 

 final stages in the process of oxidation and breakdown of the fatty acids. 

 For the stages between, we can only surmise. As pointed out by Leathes 

 the introduction of double bonds produces points of weakness in the long 

 chains where oxidation with subsequent breaking readily takes place, pro- 

 ducing shorter chain mono- and dicarboxy acids. (In this connection it 

 is interesting to note that in such a process of oxidation and breaking 

 down, only one monocarboxy acid would be produced from a long chain 

 fatty acid, the other fragments being dicarboxy acids. Thus from an un- 

 saturated fatty acid of the linoleic series such as Hartley finds in the liver, 



H H H H 



CH 3 . (CH 2 ) 4 . C = C . CH 2 . C = C . (CH 2 ) 7 . COOH 



there would be formed, 



CH 3 . (CH 2 ) 4 . COOH CH 2 . (COOH) 2 (CH 2 ) 7 . (COOH) 2 

 caproic acid malonic acid and azelaic acid 



of which the dicarboxy acids would presumably have a different type of 

 metabolism from the monocarboxy acids.) 



