THE ESSENTIAL DUCTLESS GLANDS 229 
of the life of the body—the growth, the sexuality, the 
emotions, the immunity—one wonders whether, after 
all, this avalanche of literature is keeping pace with the 
interest that the subject deserves. 
In a short essay, limited in scope and space, one can- 
not go into the details of this subject. Those who look 
for details are referred to the substantial works of A. 
Biedl, “The Internal Secretory Organs; Their Physi- 
ology and Pathology;’” Sajous’ ‘Internal Secretions 
and Principles of Medicine ;’’ Swale Vincent’s “Internal 
Secretion and the Ductless Glands;” Falta’s “Ductless 
Glandular Diseases ;” Harrower’s “Practical Hormone 
Therapy,” and numerous other works. In this essay 
we will, therefore, merely outline rather roughly the 
salient points regarding some of the endocrine glands 
and their influence upon the organism and conclude 
with a brief mention of some of the potentialities that 
those glands hold out to us in the nearest future. 
THE HORMONE PRODUCING ORGANS 
As their name implies, the ductless glands are organs 
whose products, called hormones, have no outlet into 
the free surfaces of the organism, like ordinary glands 
do, but instead find their way directly into the blood 
stream, which, laden with such hormones, exerts its 
specific influence upon the living organism. Hence the 
term, “internal secretion.” The branch of medicine 
that makes a study of the ductless glands and their in- 
ternal secretions is called “endocrinology.” The most 
known, because the most studied glands of this type, 
are the thyroid, parathyroids, adrenals, pituitary and 
gonads (testicles and ovaries). Others, perhaps less 
well known in their action, are the thymus, pancreas, 
spleen and pineal gland. 
It seems that Nature, in her wise ways, fully appre- 
ciated the importance and value of these small organs 
in placing them in inaccessible corners of the organism, 
