164 STORRS AGRICULTURAL EXPERIMENT STATION. 
The digestion proper, by which we understand the changes 
which the food undergoes in the digestive canal in order to fit 
the digestible portion to be taken into the body and lymph and 
do its work as nutriment, is essentially a chemical process. 
About this a great deal has been learned within comparatively 
few years, although but comparatively little of the results has 
yet found its way into current literature. 
The subject studied in the experiments here reported is a 
still different one. It has to do with the quantities of material 
actually digested from food as ordinarily eaten. ‘The question 
is, What proportion of each of the nutrients in different food 
materials is actually digestible? In meat or bread, for instance, 
what percentages of the total protein, fats, and carbohydrates 
will be ordinarily digested by a healthy person, and what pro- 
portion of each will escape digestion ? 
The proportions of food constituents digested by domestic 
animals have been‘a matter of active investigation in European 
agricultural experiment stations during the past thirty years. 
During the past fifteen years not a little has been done in some 
stations in the United States. The experiments on digestion 
by sheep carried out by the Storrs Station belong to this class. 
The method consists in weighing and analyzing both the food 
consumed and the intestinal excretion. Since the latter rep- 
resents very nearly the amount of food undi gested, if we subtract 
it from the whole amount taken into the body the difference 
will be the amount digested. 
Such experiments upon human subjects, however, are ren- 
dered much more difficult by the fact that in order that the 
digestibility of each particular food material may be determined 
with certainty, it must not be mixed with other materials, 
Hence the diet during the experiments must be so plain and 
simple as to make it extremely unpalatable. An ox will live 
contentedly on a diet of hay for an indefinite time, but for an 
ordinary man to subsist a week on meat or potatoes or eggs is 
a very different matter. No matter how palatable such a 
simple food may be, at first, to a man used to the ordinary diet 
of a well-to-do community, it will almost certainly become 
repugnant to him ina few days. In consequence, the diges- 
tive functions are disturbed and the accuracy of the trial 
impaired, a fact, by the way, which strikingly illustrates the 
importance of varied diet in civilized life. 

