constipation.

It is difficult to determine how much of a food is unassimilated in the
body. This is for the reason of the intestinal refuse consisting not only
of undigested food, but also of residues of the digestive juices, mucus
and epithelial debris. These latter have been shown to amount to from
one-third to one-half of the whole of the fæces, which is much more than
had previously been supposed.

John Goodfellow has shown that of very coarse wholemeal bread quite 14 per
cent. was undigested, whilst bread made from ordinary grade wholemeal
showed 12.5 per cent. Such a method of analysis was adopted as it was
believed would exclude other than the food waste. The experiments were
made on a person who was eating nothing but the bread. It seems probable
that a smaller proportion would have remained unassimilated had the bread
not formed the sole food. It is advisable that wheatmeal he ground as
finely as possible, the coarse is not only to a less extent assimilated
but apt to irritate the bowels. Notwithstanding that fine white bread gave
only 4.2 per cent. and a coarse white bread 4.9 per cent. of waste, a fine
wheatmeal bread is more economical as the same quantity of wheat produces
a greater weight of flour richer in proteid and mineral matter. From a
large number of experiments with man, it has been calculated that of
proteids there is digested when animal food is eaten 98 per cent., from
cereals and sugars 8 per cent., from vegetables and fruits 80 per cent.
The difference between the proportions digested of the other food
constituents was much less. Although there is here a theoretical advantage
in favour of animal food, there are other considerations of far more
importance than a little undigestible waste. The main question is one of
health. In some dietary experiments of a girl aged 7, living upon a fruit
diet, of whom we have given some particulars elsewhere, Professor Jaffa