ow the
attempt to destroy the intestinal microbes by the use of chemical agents
has little chance of success, and the intestine itself may be harmed
more than the microbes. If, however, we observe the new-born child we
find that, when suckled by its mother, its intestinal microbes are very
different and much fewer than if it be fed with cows' milk. I am
strongly convinced that it is advantageous to protect ourselves by
cooking all kinds of food which, like cows' milk, are exposed to the
air. It is well-known that other means--as, for instance, the use of
lactic acid--will prevent food outside the body from going bad. Now as
lactic fermentation serves so well to arrest putrefaction in general,
why should it not be used for the same purpose within the digestive
tube? It has been clearly proved that the microbes which produce lactic
acid can, and do, control the growth of other microbes within the body,
and that the lactic microbe is so much at home in the human body that it
is to be found there several weeks after it has been swallowed.

From time immemorial human beings have absorbed quantities of lactic
microbes by consuming in the uncooked condition substances such as
soured milk, kephir, sauerkraut, or salted cucumbers, which have
undergone lactic fermentation. By these means they have unknowingly
lessened the evil consequences of intestinal putrefaction. The fact that
so many races make soured milk and use it copiously is an excellent
testimony to its usefulness, and critical inquiry shows that longevity,
with few traces of senility, is conspicuous amongst peoples who use sour
milk extensively.

A reader who has little knowledge of such matters may be surprised by my
recommendation to absorb large quantities of microbes, as the general
belief is that microbes are all harmful. This belief, however, is
erroneous. There are many useful microbes, amongst which the lactic
bacilli have an honourable place. If it be true that our precocious and
unhappy old age is due to poisoning of the tissues, the greater part of
the poison coming from the large intestine, inhabited by numberless
microbes, it is clear that agents which arrest intestinal putrefaction
must at the same time postpone and ameliorate old age. This theoretical
view is confirmed by the collection of facts regarding races which live
chiefly on soured milk, and amongst which great ages are common.

_IV.--An Ideal Old Age_

As I have shown in the "Nature of Ma