24 BULLETIN 613, U. S. DEPARTMENT OF AGRICULTURE. 
On an average the four subjects who assisted in the study of the 
digestibility of turtle fat ate 22 grains of protein. 49 grams of fat, 
and 402 grams of carbohydrate daily. The digestibility of the diet 
as a whole was found to be, for protein 57.6 per cent, for fat, 93.3 
per cent, and for carbohydrate, 96.6 per cent. When allowance is 
made for metabolic products and undigested fat resulting from the 
basal ration, the figure, 93.3 per cent, for the digestibility of the total 
fat of the diet, becomes 98.6 per cent for the digestibility of turtle 
fat alone. In reports of their physical condition the subjects made 
no reference to any laxative effect or other digestive disturbance 
resulting from the diet. Accordingly, it may be assumed that green- 
turtle fat taken in quantities not exceeding 50 grams daily is well 
tolerated and very completely assimilated by the body. 
SUMMARY. 
As a group the fats which are considered in the present paper are 
not extensively used in the home as separate fats, but all are included 
to a greater or less extent in the American dietary. Two of them, 
oleo oil and oleo stearin, find large commercial uses in the manu- 
facture of fats for domestic consumption, oleo oil being used in the 
manufacture of oleomargarin and oleo stearin in the manufacture 
of shortening fats. Since little, if any, information was available 
regarding the extent to which they are utilized by the human body, 
their coefficients of digestibility were determined and found to be 
98.4 per cent for goat's butter, 95.3 per cent for kid fat, 93.7 per 
cent for hard-palate fat, 93.9 per cent for horse fat, 96.8 per cent for 
oleo oil, 80.1 per cent for oleo stearin, 93.5 per cent for ox-marrow fat, 
96.6 per cent for ox-tail fat, and 98,6 per cent for turtle fat. 
The studies of the digestibility of fats here reported include four 
experiments with goat's butter, three experiments with kid fat, three 
experiments with hard-palate fat, three experiments with horse fat, 
eight experiments with oleo oil, three experiments with oleo stearin, 
four experiments with- ox-marrow fat, three experiments with ox-tail 
fat, and four experiments with green-turtle fat. 
The subjects ate per day on an average 42.8 grams of goat's butter, 
59.7 grams of kid fat, 87.7 grams of hard-palate fat, 62.9 grams of 
horse fat, 56.8 grams of oleo oil, 66.2 grams of oleo stearin, 86.8 grams 
of ox-marrow fat, 74.5 grams of ox-tail fat, and 46.5 grams of turtle 
fat. 
In the reports of their physical condition during the test periods, 
the subjects did not note any physiological disturbances except in 
the case of ox-marrow fat, which seemed to have a slight laxative 
effect. No evidence was secured as to whether this condition resulted 
