INTRODUCTION

The articles here presented are modern and unhackneyed.  Selected primarily as models for teaching the methods of exposition employed in the explanation of mechanisms, processes, and ideas, they are nevertheless sufficiently representative of certain tendencies in science to be of intrinsic value.  Indeed, each author is a recognized authority.

Another feature is worthy of mention.  Although the material covers so wide a field—­anatomy, zoölogy, physics, psychology, and applied science—­that the collection will appeal to instructors in every type of college and technical school, the selections are related in such a way as to produce an impression of unity.  This relation is apparent between the first selection, which deals with the student’s body, and the third, which deals with another organism in nature.  The second and fourth selections deal with kindred aspects of modern industry—­the manufacture of paper and the Linotype machine, by which it is used.  The fifth selection is a protest against certain developments of the industrial regime; the last, an attempt to reconcile the spirit of science with that of religion.  While monotony has been avoided, the essays form a distinct unit.

In most cases, selections are longer than usual, long enough in fact to introduce a student to each field.  As a result, he can be made to feel that every subject is of importance and to realize that every chapter contains a fund of valuable information.  Instead of confusing him by having him read twenty selections in, let us say, six weeks, it is possible by assigning but six in the same period, to impress him definitely with each.

The text-book machinery has been sequestered in the Biographical and Critical Notes at the end of the book.  Their character and position are intended to permit instructors freedom of treatment.  Some may wish to test a student’s ability in the use of reference books by having him report on allusions.  Some may wish to explain these themselves.  A few may find my experience helpful.  For them suggestions are included in the Critical Notes.  In general, I have assumed that instructors will prefer their own methods and have tried to leave them unhampered.

THE EXPOSITION OF A MECHANISM

The levers of the human body[1]

Sir Arthur Keith

In all the foregoing chapters we have been considering only the muscular engines of the human machine, counting them over and comparing their construction and their mechanism with those of the internal-combustion engine of a motor cycle.  But of the levers or crank-pins through which muscular engines exert their power we have said nothing hitherto.  Nor shall we get any help by now spending time on the levers of a motor cycle.  We have already confessed that they are