Fatty acids from the egg and abdominal fats of hens given diets with no added oil, or with the inclusion of sperm oil or linseed oil contained polyethylenic acids in the "pro-absorptive" state. The dietary fat had a marked effect on the amt. of polyethylenic acids present in the egg and abdominal fats as revealed by spectroscopic examination after refluxing with KOH. The inclusion in the diet of tung oil which absorbs intensely at 270 m[mu] caused a marked increase in the preformed spectroscopic absorption at 230 m[mu] in the egg and body fatty acids. This change is probably to be ascribed to the loss of one of the conjugated unsaturated linkages of elaeostearic acid. There are evidently marked differences in the treatment of polyethylenic acids by the cow and the hen.