on the same principle. Every
trade and calling has its technical terms. The meaning of these terms
is hidden from the rest of the world, but the origin of their
existence is not difficult to explain. The jargon of the criminal
arises from the same causes and is constructed on exactly the same
principles as the technical words and phrases of the man of science.
When a man of science is compelled to make frequent use of a phrase,
he generally gets rid of it by inventing some technical word; it is
precisely the same with criminals. With them technical words are used
instead of phrases, and short words instead of long ones in all
matters where criminal interests are intimately concerned, and on all
topics which are habitually the subjects of conversation among the
criminal classes. The language of the Stock Exchange with its Bulls,
Bears, Contangos, and other short and comprehensive expressions for
various kinds of stocks, is on all fours with the slang of criminals,
and it is not necessary to resort to atavism in order to explain it.
It arises to supply professional needs, and criminal argot springs up
from exactly the same cause.

Summing up our inquiries respecting the criminal type we arrive, in
the first place, at the general conclusion, that so far as it has a
real existence it is not born with a man, but originates either in the
prison, and is then merely a prison type, or in criminal habits of
life, and is then a truly criminal type. As a matter of fact, the two
types are in most cases blended together, the prison type with its
hard, impassive rigidity of feature being superadded to the gait,
gesture and demeanour of the habitual criminal. In combination these
two types form a professional type and constitute what Dr. Bruce
Thomson[41] has called "a physique distinctly characteristic of the
criminal class." It is not, however, a type which admits of accurate
description, and its practical utility is impaired by the fact that
certain of its features are sometimes visible in men who have never
been convicted of crime. The position of the case, with respect to the
criminal type, may be best described by saying that an experienced
detective officer will be sure in nine cases out of ten that he has
got hold of a criminal by profession, but in the tenth case he will
probably make a mistake. In other words, face, manner and demeanor are
no infallible index of character or habits of life.

[41] _Journal of Mental Scie