14 BULLETIN 310, U. S. DEPARTMENT OF AGRICULTURE. 
BUTTER. 
Many investigators have studied the digestibility of butter under a 
vide variety of conditions, because of its very extensive use in coun- 
tries where it is obtainable at relatively low prices. In a number of 
the earlier determinations the rations used consisted of only one food 
material in addition to the butter. 
Kubner, 1 as a part of an extended series of experiments, determined 
the digestibility of a simple ration of butter and potatoes, and of one 
made up of green beans (540.2 grams) and butter (53.4 grams). 2 The 
coefficient of digestibility of fat in the first case was 96.3 per cent and 
in the second 91.5 per cent. In another test, 3 with a ration contain- 
ing a considerably larger proportion of fat — 240 grams of butter — 
daily, this fat was 97.3 per cent assimilated. 
Atwater, 4 in studies made previous to his connection with the 
nutrition investigations of the Department of Agriculture, studied a 
simple diet of fish (1,584 grams) and butter (30.5 grams), and found 
that the fat had a coefficient of digestibility of 91 per cent. 
A similar experiment by Mali atti 5 is reported in which polenta (a 
porridge made of Indian corn meal and butter), supplying 92.5 grams 
of fat per day, was used. The coefficient of digestibility of the fat of 
the corn meal alone was found to be 57.86 per cent, while the butter, 
which supplied by far the greater part of the fat content of the ration, 
was 97.7 per cent available. 
The variation in digestibility as determined by the different investi- 
gators is doubtless due to a lack of uniformity of conditions under 
which the experiments were performed. The results of these early 
experiments, however, agree fairly well in showing that butter is very 
completely digested. In later experiments, which are also of interest, 
a more complex basal ration seems to have been used. 
Mayer 6 studied the thoroughness of the digestion of butter by a 
39-year-old man and a 9-year-old boy, who were given butter in a sim- 
ple mixed diet. The average digestibility of butter as determined 
by three experimental periods, each of three days' duration, was for 
the man 98 per cent and for the boy 97 per cent. 
Bertarelli 7 investigated the nutritive value of butter, using three 
healthy men as subjects for one experimental period each. He ob- 
tained 94 per cent as an average digestibility. 
Huldgren and Landergren 8 used a simple basal ration of rye bread 
made of rye flour, water, and yeast and baked in hard, thin cakes. 
i Ztschr. Biol., 15 (1879), No. 1, pp. 136-147. 
2 Idem, 16 (1880), No. 1, p. 127. 
3 Idem, 15 (1879), No. 1, pp. 174-176. 
« Idem, 24 (1887), No. 1, p. 16. 
6 Sitzber. K. Akad. Wiss. [Vienna], Math. Naturw. Kl., 90 (1884), III, No. 5, pp. 328-335. 
= Landw. Vers. Stat., 29 (1883), pp. 215-232. 
' Riv. Ig. e. Sanit. Pub., 9 (1898), Nos. 14, pp. 538-545; 15, pp. 570-579. 
8 Skand. Arch. Physiol., 2 (1890), No. 4-5, pp. 373-393. 
