hirty, it is said)
have been published in the last quarter of a century, a fact which has
now and then been deplored by the pessimistic critic.[27] Few share
this opinion, however. The textbooks have, to be sure, often served,
not to unfold a consistent system of thought, but to reveal the lack
of one. But they have afforded to the teachers and students, in a
period of developing conceptions on the subjects, a wide choice of
treatment of the principles much more exactly worked out and carefully
expressed than is possible through the medium of lectures as recorded
in the students' hastily written notes.

Questions, exercises, and test problems are widely used as supplementary
material for classroom discussion.[28] Separately printed collections of
such material date back at least to W. G. Sumner's _Problems in
Political Economy_ (1884), which in turn acknowledged indebtedness to
other personal sources and to Milnes' collection of two thousand
questions and problems from English examination papers. With somewhat
varying aims, further commented upon below, and in varying degrees, all
teachers of economics now make use of such questions in their teaching
of both general and special courses. Unquestionably there are, in the
use of the problem method, possibilities for good which few teachers
have fully realized.[29]

The selection and arrangement of materials for supplementary readings
is guided by various motives, more or less intermingling. It may be
chiefly to parallel a systematic text by extracts taken largely from
the older "classics" of the subject (as in C. J. Bullock's _Selected
Readings in Economics_, 1907); or to provide additional concrete
material bearing mostly upon present economic problems (as in the
author's _Source Book in Economics_, 1912); or to supplement a set of
exercises and problems (as in F. M. Taylor's _Some Readings in
Economics_, 1907); or to constitute of itself an almost independent
textbook of extracts, carefully edited with original introductions to
chapters (as Marshall, Wright, and Field's _Materials for the Study of
Elementary Economics_, 1913, and W. H. Hamilton's _Readings in Current
Economic Problems_, 1914).

Whatever be the particular tool of instruction, whether lecture,
textbook with classroom discussion, problem study, or collateral
readings, its use may be very different according as the teacher seeks
to develop the subject positively or negatively, to present a single
definit