cy expert, "if you are going to call on me
constantly to stiffen that jaw I'll fix it so it will stay that way and
save myself the trouble."

Inheritance of Acquired Traits

Thus the more combative jaw, having become permanent in the man's
organism, can be passed on to his children.

Right here comes a most interesting law and one that has made possible
the science of Human Analysis:

Law of Size

_The larger any part or organ the better its equipment for carrying
out the work of that organ and the more does it tend to express itself._
Nature IS an efficiency expert and doesn't give you an oversupply of
anything without demanding that you use it.

Jaws Becoming Smaller

Our ancestors developed massive jaws as a result of constant combat.
As fast as civilization decreased the necessity for combat Nature
decreased the size of the average human jaw.

Meaning of the Big Jaw

But wherever you see a large protruding jaw you see an individual
"armed and engined," as Kipling says, for some kind of fighting. The
large jaw always goes with a combative nature, whether it is found on a
man or a woman, a child, a pugilist or a minister.

Exhibit A--The Irishman

The large jaw, therefore, is seen to be both a result and a cause of
certain things. As the inheritance of a fighting ancestor it is the
result of millions of years of fighting in prehistoric times, and, like
any other over-developed part or organ, it has an intense urge to
express itself. This inherent urge is what makes the owner of that jaw
"fight at the drop of the hat," and often have "a chip on his shoulder."

Natural Selection

Thus, because every external characteristic is the result of natural
laws, and chiefly of natural selection, the vital traits of any creature
can be read from his externals. Every student of biology, anatomy,
anthropology, ethnology or psychology is familiar with these facts.

Built to Fit

Man's organism has developed, altered, improved and evolved "down
through the slow revolving years" with one instinctive aim--successful
reaction to its environment. Every part has been laboriously constructed
to that sole end. Because of this its functions are marked as clearly
upon it as those of a grain elevator, a steamship or a piano.

Survival of the Fittest

Nature has no accidents, she wastes no material and everything has a
purpose. If you put up a good fight to live she will usually come to
your rescue and giv