PAT METABOLISM 705 



to acl od unsaturated fatty acids in tl old, it causes hydroxy] groups 



Ik- introduced in the position oi the double bonds. When the oxidation is 



formed al a moderate temperature, the fatty acid falls apart at the 

 hydroxy] groups. A fatty acid with eighl hydroxy] groups lias been 

 obtained in this way from the liver of the pig. The presence of the hy- 

 droxy] groups has been confirmed by finding thai an octobromide is ob- 

 tained by treatment with bromine. An acid of the same formula is said t<> 

 be presenl in cod-liver oil. Te sum up, we may conclude thai there are 

 certain positions, in the chains of carbon atoms which constitute the fatty- 

 acid radicle, where the liver introduces double bonds, and thai tin- weak- 

 ened radicles then circulate to the tissues, where they break u]> at tl 



itions. 



Bui this is probably nol the only way in which the liver assists in 

 the metabolism of fat. It may also lake pari in the building of fatty- 

 acid radicles into the complex molecule of lecithin. The process of de- 

 saturation thai we have just considered is probably a preliminary step 

 to this incorporation of the fatty-acid molecule into lecithin, for it is 

 well known that lecithin contains highly unsaturated fatty-acid radi- 

 cles. In support of such a view it is interesting to note that in alcohol- 

 ether extracts from normal and pathological livers, the lecithins, which are 

 precipitated by acetone, have higher iodine values i. e., are more ui 

 urated than the neutra] fats extracted from the same liver, which also 

 have higher iodine values than the depol fal of the same animal. The 

 desaturation process must, therefore, involve the fatty acids before t ; 

 become built into the lecithin molecule. 



The liver is probably not the only place in the animal body where the 

 desaturation of fatty acids i> broughl about. The relative activity of 



the different tissues in this regard has 1 ii studied by feeding cats 



with fatty fish and then determining the iodine value of fa1 from various 

 places in the body. The absorbed fal was more obvious in the fiver than 

 hi the subcutaneous tissues, because it had not become diluted with fat 



deposited it may have keen months previously, which would he the 



le in the fat of the tat depots: and it was found that, although the 



iodine value of the subcutaneous fat was slightly raised, that of the 



liver was much more so, indicating that the desaturation process had 



I n more active in this organ, hut had als !CUrr< a certain extent 



in the depots. 



Before leaving this subjed of fat in the liver, it is important I 

 call the old observation of Rosenthal, that a more or less recipi 

 relationship exists between glycogen and fat in the liver. When much 

 glycogen is presenl th< little or > and v 1' is ita] 



