Yet all this time the old method of inductive observation has not gone
dead. Most magnificent triumph of nineteenth century science, the
evolution theory of Charles Darwin, remains the most conspicuous
instance of clarification of thought in human history. That work was
the outcome of an attempt to relate and interpret a collection of
observations on species and their variations, that had long lain to
hand, a mixture without a solvent. Darwin saw certain generalizations
as solvents, and behold! a clear solution out of the mud. But it was
by piling evidence upon evidence, co-ordinating isolated facts not
directly associated, that the towering structure was erected. There is
no prettier sample extant of the powers of the inductive method.

Not that there are no triumphs of the quantitative method in store for
the biologist. Already, the materials of the Mendelians have become
basic parts of his structure. And today, in pursuit of the solutions
of hundreds of the problems of living matter, chemists and
physiologists are employing the most precise standards, units, and
measures of the physical sciences. Blood chemistry of our time is a
marvel, undreamed of a generation ago. Also, these achievements are
a perfect example of the accomplished fact contradicting a priori
prediction and criticism. For it was one of the accepted dogmas of the
nineteenth century that the phenomena of the living could never be
subjected to accurate quantitative analysis.

However desirable the purely quantitative experimental methods may be,
they naturally need always to be preceded by the qualitative studies
of direct observations. Inevitably there will be numberless errors,
apparent and real inconsistencies and contradictions, and ideas that
will have to be discarded. Just the same there is no other method of
progress. Every bit of evidence points towards the internal secretions