208 W. K. BLOOR 



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

 the organism the probable correctness of Loathes* hypothesis as regards 

 desaturation must be admitted. That phosphorization takes place in other 

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

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

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

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

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

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

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

 organs and tissues esterases which hydrolyze lecithin readily but which 

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

 in the living organism is well shown by the work of Meigs and coworkers, 

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

 in lecithin in the blood passing through the mammary gland. 



Later Stages P-oxidation. As regards later stages in the inter- 

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

 ordinarily disappear in metabolism without leaving any traces in the way 

 of intermediate stages by which the process of breakdown may be followed. 

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

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

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

 butyrie and diacetic acids which with their derivative acetone constitute 

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

 breakdown of the fatty acids is- strongly indicated by the work of Jvnoop, 

 whose hypothesis of p-oxidation seems to account satisfactorily for the 

 final stages in the proce3s 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 cf 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 moiiocarboxy acid would be produced from a long chain 

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

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



II II H H 



CH 3 . (CH 2 ) 4 . C C . CH 2 .0 = 0. (OH 2 ) T . COOH 



there would be formed, 



CH 5 . (CH 2 ) 4 . COOH CH 2 . (COOH) 2 (CIL.) 7 . (COOH) 2 

 caproic acid ' rnalonic acid and azclaic acid 



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

 metabolism from the moiiocarboxy acids.) 



