FAT METABOLISM 699 



BLOOD LIPOIDS IN NORMAL AND IN DIABETIC PERSONS 



It will be observed that there is about 0.7 per cent of total fatty sub- 

 stances in normal blood. The fatty acids (palmitic and oleic) amount to 

 about 0.4 per cent, and are equally distributed between plasma and 

 corpuscles; the lecithin, about 0.3 per cent, being twice as abundant in 

 corpuscles as in plasma, and the cholesterol, 0.2 per cent, about equally 

 distributed. In diabetes all of these substances are seen to be increased 

 in proportion to the severity of the disease, the increase being mostly 

 in the plasma. The increase in cholesterol (confined mainly to the 

 plasma) is particularly interesting, since the substance is unaffected in 

 amount by excessive feeding with fat. 



The Destination of the Fat of the Blood. In general, it may be said 

 that the blood fat is transported to three places: (1) the depots for fat; (2) 

 the liver; and (3) the tissues. The fat present in each of these places 

 differs from that in the others, as is revealed by chemical examination 

 by the methods described on page 687. The depot fat usually yields about 

 95 per cent of its total weight as fatty acid. The tissue fat, on the other 

 hand, yields only about 60 per cent of its total weight as fatty acid. 

 This difference indicates that the fatty acid must be combined in the 

 tissues with a much larger molecule than is the case in the fat of the 

 depots. This large molecule is probably that of lecithin or other phos- 

 pholipin, and the smaller molecule in the depots, that of neutral fat. 

 The liver fat takes an intermediate position between depot fat and tissue 

 fat in its yield of fatty acid. When no active metabolism of fat is go- 

 ing on, the liver fat is like that of the tissues ; but when fat metabolism 

 is active, the liver fat occupies an intermediate position between liver 

 fat and depot fat. 



