Under their influence the whole of the proteins of the
food are completely dissolved and converted into simpler
bodies capable of being absorbed into the blood stream
and distributed to the tissue. Under the influence of the
pancreatic ferments the starches are further changed into
dextrine, and maltose, and under the further agency of the
intestinal juice into dextrose (sugar), in which form the
starches are absorbed into the system. Here also the fats
are split up under the influence of the pancreatic secretion,
aided by the bile, into a form capable of absorption by
the vessels. The salts and water) of the food are absorbed
unchanged.
Throughout the whole of the small intestines active secre-
tion and absorption are taking place, so that the amount of
water in the intestinal contents in the lower part of the small
intestine is about the same as in the upper part. The con-
tents of the lower part acquire a distinct faecal odour from
putrefactive products produced by the action of bacteria on
the proteins of the food. In the large intestine the process
of absorption predominates over those of secretion ; hence
that part of the intestinal contents which has not been
absorbed becomes less and less watery, and acquires the
character of faeces, in which form it is periodically expelled
from the body. The faeces consist mainly of the indigestible



22



THE BOOK OF DIET.
residue of the food, and of substances which have been
taken in too large quantities to be digested ; they also contain
various forms of bacteria.
Time Occupied by Digestion in the Stomach. — An ordi-
nary meal requires from four to six hours' digestion in the
stomach, but the time required varies with —

1. The nature and amount of the food.
