DIGESTIBILITY OF SOME ANIMAL FATS. 
21 
severe muscular activity, but should meet the needs of those follow- 
ing sedentary occupations. 
It is interesting to know whether or not the presence in the diet of 
the different fats in considerable quantity affects the digestibility of 
the other constituents and the coefficient of availability of the ration 
as a whole. It has been shown by work previously reported 1 that the 
total available energy and the ' ' coefficient of availability of energy " can 
be calculated with reasonable accuracy. The average coefficients of 
availability of energy for the rations as calculated were 93.0 per 
cent, 92.7 per cent, 91.5 per cent, and 93.9 per cent for the diets 
containing lard, beef fat, mutton fat, and butter, respectively. 
These values agree with one another closely and are somewhat higher 
than the value 91 per cent which has been found to represent the 
coefficient of availability of energy of the ordinary mixed diet. 2 It 
is reasonable to conclude, therefore, that the different fats did not 
exercise any unusual effect upon the digestibility of the other con- 
stituents of the rations. 
The statement has frequently been made that the coefficients of 
digestibility of fats are directly related to the corresponding melting 
points. The melting points of samples of the fats studied or of samples 
of fats similarly prepared are reported in the table below together 
with a compilation of values 3 determined by several investigators 
giving, presumably, the average range found in samples fairly 
true to name. The variation in the melting points of different 
samples of the same fat is consistent with the view that the melting 
points differ with the part of the body in which the fat is found and 
also with the animal from which it is taken. 
Comparison of digestibility and melting point. 
- 
Coefficient of digesti- 
bility. 
Melting point. 
Fat studied. 
Deter- 
mined. 
With allow- 
ance for 
metabolic 
products. 
Authors' 
determina- 
tions. 
Compiled 
average 
values.* 
Butter fat 
Per cent. 
94 
94 
89 
80 
Per cent. 
97 
97 
93 
88 
Degrees C. 
32.0 
35.0 
45.0 
50.0 
Degrees C. 
28-36 
Lard 
30-44 
Beef fat 
42 50 
Mutton fat 
47-49 
1 Allen's Commercial Organic Analysis. Philadelphia: Blakiston's Son & Co., 1910, 4. ed., vol. 2, p. 72. 
It seems fair to conclude that of those tested the fats of low melting: 
points are capable of more complete assimilation than those which 
have a high melting point. 
1 Connecticut Storrs Sta. Bpt. 1899, p. 104. 
2 U. S. Dept. Agr., Expt. Sta. Bui. 136 (1903), p. 113. 
8 Allen's Commercial Organic Analysis. Philadelphia: Blakiston's Son & Co., 1910, 4. ed., vol. 2, p. 72. 
