has become stereotyped in his reactions. Nature's solution of this
_impasse_ is death. Death insures the continual removal of the no longer
adjustable, and the places of those who die are filled by new material
capable of the new demands. But it is the means that nature takes to
secure the renewal of material still capable of adjustment that is of
significance. From each adult sometime during the course of his life
nature provides that a small bit shall be detached which, in the higher
animals, in union with a similar detached bit of another individual will
develop into a child and ultimately be ready to replace the adult when
he becomes senile and dies. Life is thus maintained by a continuous
stream of germ plasm and is not periodically interrupted in its course,
as it seems to be, by death.

The characteristics of this detached bit of germ plasm are interesting.
It does not manifest any of that complicated structure which we meet
with in the other parts of the body. The several parts of the body are
highly differentiated, each for a specific function. Gland cells are
developed to secrete, muscle cells to contract, bone cells to withstand
mechanical stresses, etc. Manifestly development along any one of these
lines would not produce an individual possessing, in its several parts,
all of these qualities. Development has to go back of the point of
origin of these several variations in order to include them all. In
other words, regeneration has to start with relatively undifferentiated
material. This is excellently illustrated by many of the lower,
particularly the unicellular, animals, in which reproduction is not yet
sexual, but by the simple method of division. A cell comes to rest,
divides into two, and each half then leads an independent existence.
Before such a division and while the cell is quiescent--in the resting
stage, as it is called--the differentiations of structure which it had
acquired in its lifetime disappear; it becomes undifferentiated,
relatively simple in structure. This process has been called
dedifferentiation. When all the differentiations which had been acquired
have been eliminated, then division--rejuvenescence--takes place.

From this point of view we may see in war the preliminary process of
rejuvenescence. International adjustments and compromises are made until
they can be made no longer; a condition is brought about which in Europe
has been termed the balance of power, until the situation