6 BULLETIN 630, IT. S. DEPARTMENT OF AGRICULTURE. 



The coefficient of digestibility of almond oil as determined by these 

 experiments is. for all practical purposes, identical with the coeffi- 

 cient of digestibility, 97 per cent, reported in an earlier paper 1 of this 

 series for the most widely used animal fats, butter, and lard. 



BLACK-WALNUT OIL. 



Black-walnut oil, which is obtained from the nuts of Juglans nigra, 

 is commercially classified as a drying oil. When free from fatty 

 acid, it is said to be preferred to any other oil for making artists' 

 white paints, since it makes them less liable to crack than if prepared 

 with linseed oil. Black walnuts are rich in oil, 2 56 per cent being 

 contained in the edible portion, and when subjected to pressure yield 

 a yellow oil possessing the characteristic odor and flavor of the nuts. 

 Although this flavor is esteemed by many, it is somewhat too pro- 

 nounced to make this oil as generally adaptable for cooking or salad 

 purposes as the others here considered. 



A supply of first quality nuts was obtained from a local dealer. 

 The kernels were ground in a common household meat chopper, after 

 which the oil was extracted by hydraulic pressure without heating; 

 approximately a 50 per cent yield resulting. 



In all other determinations of the coefficients of digestibility of the 

 many fats included in this series, the basal ration served in conjunc- 

 tion with the blancmange, which contained the fat under considera- 

 tion, consisted of wheat biscuit, fruit, sugar, and tea or coffee if de- 

 sired. The basal ration served in the experiments with the black- 

 walnut oil was of a slightly different composition, because, owing to 

 the exhaustion of the available supply of the wheat biscuit, it be- 

 came necessary to replace them by crackers. However, since the com- 

 position of the crackers was quite similar to that of the wheat biscuit, 

 it is not thought that this change in the basal ration has in any way 

 vitiated the values obtained in these experiments for comparison with 

 values obtained for the digestibility of other oils studied. 



Four young men of normal health and activity served as subjects 

 for the tests made with the black-walnut oil; the following tables 

 contain the essential data for interpreting the results obtained. 



!U. S. Dept. Agr. Bui. 310 (1915). 



2 U. S. Dept. Agr., Office Espt. Stas. Bui. 28 (1906), rev. ed. 



