ying forms of matter
have been evolved?

But the discovery of electrons is only one of the revolutionary changes
which give modern science an entrancing interest.

As in chemistry and physics, so in the science of living creatures there
have been recent advances that have changed the whole prospect. A good
instance is afforded by the discovery of the "hormones," or chemical
messengers, which are produced by ductless glands, such as the thyroid,
the supra-renal, and the pituitary, and are distributed throughout the
body by the blood. The work of physiologists like Professor Starling and
Professor Bayliss has shown that these chemical messengers regulate what
may be called the "pace" of the body, and bring about that regulated
harmony and smoothness of working which we know as health. It is not too
much to say that the discovery of hormones has changed the whole of
physiology. Our knowledge of the human body far surpasses that of the
past generation.

The persistent patience of microscopists and technical improvements like
the "ultramicroscope" have greatly increased our knowledge of the
invisible world of life. To the bacteria of a past generation have been
added a multitude of microscopic _animal_ microbes, such as that which
causes Sleeping Sickness. The life-histories and the weird ways of many
important parasites have been unravelled; and here again knowledge means
mastery. To a degree which has almost surpassed expectations there has
been a revelation of the intricacy of the stones and mortar of the house
of life, and the microscopic study of germ-cells has wonderfully
supplemented the epoch-making experimental study of heredity which began
with Mendel. It goes without saying that no one can call himself
educated who does not understand the central and simple ideas of
Mendelism and other new departures in biology.

The procession of life through the ages and the factors in the sublime
movement; the peopling of the earth by plants and animals and the
linking of life to life in subtle inter-relations, such as those between
flowers and their insect-visitors; the life-histories of individual
types and the extraordinary results of the new inquiry called
"experimental embryology"--these also are among the subjects with which
this OUTLINE will deal.

The behaviour of animals is another fascinating study, leading to a
provisional picture of the dawn of mind. Indeed, no branch of science
surpasses in interest that whic