law is indenture--a certain form of contract. Philological researches
have uncovered an interesting history regarding this word. It seems
that in olden days when two persons made an agreement they wrote it on
two pieces of paper, then notched the edges so that when placed
together, the notches on the edge of one paper would just match those
of the other. This protected both parties against substitution of a
fraudulent contract at time of fulfillment.

Still earlier in man's development, before he could write, it was
customary to record such agreements by breaking a stick in two pieces
and leaving the jagged ends to be fitted together at time of
fulfillment. Sometimes a bone was used this way. Because its critical
feature was the saw-toothed edge, this kind of contract was called
indenture (derived from the root _dent_--tooth, the same one from which
we derive our word dentist).

The formal, legal-looking document which we today call an indenture
gives us no hint of its humble origin, but the word when analyzed by
the technique of philology tells the whole story, and throws much light
upon the legal practices of our forbears. Having discovered one such
valuable fact in philology, the student of law may be led to
investigate the science still further and find many more. As a result
still he will become interested in philology.

By this illustration we have demonstrated the first psychological law
of interest, and also its corollary which is: _State the new in terms
of the old_. For we not only gave our lawyer new information culled
from philological sources; we also introduced our fact in terms of an
old fact which was already "interesting" to the lawyer. This is
recognized as such an important principle in education that it has