DIGESTIBILITY OF SOME NUT OIL&. 13 
The average coefficient of digestibility of the total fat of the diet 
is 94.4 per cent. If proper allowance is made for the metabolic 
products and the undigested fat remaining from the basal ration it 
becomes 97.6 per cent for English- walnut oil alone. The protein and 
carbohydrate of the diet are shown to be 69.6 per cent and 97.2 per 
cent digested, respectively. 
The difference between the coefficient of digestibility, 97.6 per cent, 
obtained in these experiments and the 85 per cent or less obtained by 
Jaffa * in his series of 11 digestion experiments, in which the whole 
nuts were eaten, is thought to be due in part to the form in which 
the oil was used and may be due in part to Jaffa's considering the 
ether extract of whole nuts as fat whereas substances other than fat 
were doubtless extracted, and also may be due in part to no correc- 
tion being made for metabolic products occurring in the ether ex- 
tract of the feces. In the latter case it was taken as a constituent 
of the nut and was probably less readily and completely acted upon 
by the digestive juices than when it had been mechanically separated 
and was taken as a separated fat. 
The subjects consumed on an average 78 grams (69.9 grams, 83.8 
grams, 81.6 grams) of English-walnut oil daily. All three of the 
subjects reported a laxative effect as a result of the diet ; one experi- 
enced the effect at the beginning of the test period, one at the end, 
and one during the entire experimental period. Accordingly, it is 
believed that the limit of tolerance for this oil is not greatly in excess 
of 80 grams daily. 
HICKORY-NUT OIL. 
The oil of the hickory nut {Gary a ovata) is not separated for 
edible purposes in this country. It is not without interest to note, 
however, that the American Indians used hickory-nut oil for food 
purposes. The oil, according to Carr, 2 was obtained by mixing the 
pounded nuts in boiling water, straining off the oily liquid, and 
skimming off the oil which floated on the water in which the nuts 
were boiled. " [They] kept it in gourds or earthen pots, etc., using 
it as we do butter on their bread or to give body and flavor to their 
broth when meat was scarce." 2 
Carr also states that oil was obtained from acorns and used in a 
similar way. 
The digestibility of hickory-nut oil is of interest in view of the 
large quantities of hickory nuts eaten yearly and especially since the 
edible portion is reported 3 to contain 67 per cent of oil. 
1 Loc. cit. 
2 Proc. Amer. Antiquarian Soc, n. ser., 10 (1895), pp. 171, 172, 181. "The Food 
of Certain American Indians and their Methods of Preparing It." 
3 U. S. Dept. Age, Office Expt. Stas. Bui. 28 (1906), rev. ed., p. 75. 
