on or any other disease, or has her tissues
saturated with the toxins of this disease, it is hardly to be expected
that the development of the child will proceed with the same perfection
as it would under perfectly normal maternal surroundings.

However, even this influence is comparatively small; for one of the most
marvelous things in nature is the perfection of the barrier which she
has erected between the child before birth and any injurious conditions
which may occur in the body of the mother. Here preference, so to speak,
is given to the coming life, and whenever there is a contest for an
adequate supply of nutrition, as, for instance, in cases of underfeeding
or of famine, it is the mother who will suffer in her nutrition rather
than the child. The unborn child, biologically considered, feeds upon
the best she has to offer, rejecting all that is inferior, doing nothing
and giving nothing in return.

How perfectly the coming generation is protected under the most
unfavorable circumstances we have been given a striking object-lesson in
one family of the lower animals. In the effective crusade against
tuberculosis in dairy cattle waged by the sanitary authorities in
Denmark, it was early discovered that the greatest practical obstacle to
the extermination of tuberculosis in cattle was the enormous financial
sacrifice involved in killing all animals infected. The disease was at
that time particularly rife among the high-bred Jersey, Holstein, and
other milking breeds. It was determined as a working compromise to test
the truth of the modern belief that tuberculosis was transmitted only by
direct infection, by permitting the more valuable cows to be saved alive
for breeding purposes. They were isolated from the rest of the herd and
given the best of care and feeding. The moment that their calves were
born they were removed from them altogether and brought up on the milk
of perfectly healthy cows. The milk of the infected cows was either
destroyed or sterilized and used for feeding pigs.

The results were brilliantly successful. Scarcely one of the calves thus
isolated developed tuberculosis in spite of their highly infected
ancestry. And not only were they not inferior in vigor and perfection of
type to the remainder of their breed, but some of them have since become
prize-winners. The additional care and more abundant feeding that they
received more than compensated for any problematic defect in their
heredity.