not a single one
whose elements can become permanent constituents of the body, or exist
as long as the individual. The tumour as a whole may last; but its
individual elements perish. If we examine a tumour after it has existed
for perhaps a year, we usually find that the elements first formed no
longer exist in the centre; but that in the centre they are
disintegrating, dissolved by fatty changes. If a tumour be seated on a
surface, it often presents in the centre of its most prominent part a
navel-like depression, and the parts under this display a dense cicatrix
which no longer bears the original character of the new formation.
Heterologous new formations must be considered parasitical in their
nature, since every one of their elements will withdraw matters from the
body which might be used for better purposes, and since even its first
development implies the destruction of its parent structures.

In view of origin of new formations it were well to create a
nomenclature showing their histological basis; but new names must not be
introduced too suddenly, and it must be noted that there are certain
tumours whose histological pedigree is still uncertain.

_Printed in the United States of America_

FOOTNOTES:

[1] Azure transparent spheres conceived by the ancients to surround the
earth one within another, and to carry the heavenly bodies in their
revolutions.

[2] Book I., Prop. i. The areas which revolving bodies describe by radii
drawn to an immovable centre of force do lie in the same immovable
planes and are proportional to the times in which they are described.

Prop. ii. Every body that moves in any curve line described in a plane
and by a radius drawn to a point either immovable or moving forward with
a uniform rectilinear motion describes about that point areas
proportional to the times is urged by a centripetal force directed to
that point.

Prop. iii. Every body that, by a radius drawn to another body, howsoever
moved, describes areas about that centre proportional to the times is
urged by a force compounded out of the centripetal force tending to that
other body and of all the accelerative force by which that other body is
impelled.

[3] If the periodic times are in the sesquiplicate ratio of the radii,
and therefore the velocities reciprocally in the subduplicate ratio of
the radii, the centripetal forces will be in the duplicate ratio of the
radii inversely; and the converse.

[4] _i.e._, showi