lity. They continue to exert a powerful pressure throughout
maturity. But life episodes and crises, diseases, accidents, and
struggles, experiences of pleasure and pain, as well as climatic
factors, settle finally which endocrine or endocrines are left in
control as a consequence of the series of reactions the period of
maturity may be analyzed into.

THE INTERPRETATION OF SENILITY

Senility inevitably follows maturity, not as night follows day by a
mathematical necessity, but because of the process of degeneration
which ultimately overtakes all the glands of internal secretion,
dominant as well as subordinate. Just why the degeneration must occur
no one can say. Injury to the endocrine organs of one sort or another,
ranging all the way from emotional exhaustion to bacterial infection,
is the reason usually considered sufficient. Just why recuperation and
regeneration do not preserve them in the elderly as they do in youth
is a problem to be solved when we understand the laws of regeneration,
at present almost totally beyond our control. Some say that it is a
matter of the wear and tear of our blood vessels, those rubber-like
tubes which transport food and drainage with nonchalant equanimity to
all cells as long as they last. In the classic phrase: a man is as
old as his arteries, ergo his ductless glands will be as old as their
arteries. And the age of arteries is simply a matter of wear and tear,
the resultant of the function which is universal among molecules.
Arteriosclerosis, the hardening of arteries, might be the whole story.

But there are certain experiments and considerations which rather
confute that easy explanation, or at least make clear that the mystery
is not so simple. The work of Steinach, a Viennese investigator, has
contributed most to the elucidation of the nonarterial factor in
senility. No one has asserted more loudly the importance of the
interstitial cells that fill in the spaces between the tubules of the
testes in the male, and the follicles of the ovary in females. Rats
have been his medium of study, for they are most easily procurable,
live fastest, breed, and withstand experimental and operative
procedures better than any other animal.

An old rat is like an old man in his dotage. His bald, shrivelled skin
covers an emaciated body. His eyes are dimmed by cataracts and his
breathing is labored and difficult because his heart muscle has lost
its tone. Huddled in a corner, life to him has