introduction. The primary function of all fiction is to furnish
entertainment to the reader, and this fact has not been lost sight of.
But the interest of so-called "detective" fiction is, I believe, greatly
enhanced by a careful adherence to the probable, and a strict avoidance
of physical impossibilities; and, in accordance with this belief, I have
been scrupulous in confining myself to authentic facts and practicable
methods. The stories have, for the most part, a medico-legal motive, and
the methods of solution described in them are similar to those employed
in actual practice by medical jurists. The stories illustrate, in fact,
the application to the detection of crime of the ordinary methods of
scientific research. I may add that the experiments described have in
all cases been performed by me, and that the micro-photographs are, of
course, from the actual specimens.

I take this opportunity of thanking those of my friends who have in
various ways assisted me, and especially the friend to whom I have
dedicated this book; by whom I have been relieved of the very
considerable labour of making the micro-photographs, and greatly
assisted in procuring and preparing specimens. I must also thank Messrs.
Pearson for kindly allowing me the use of Mr. H. M. Brock's admirable
and sympathetic drawings, and the artist himself for the care with which
he has maintained strict fidelity to the text.

R. A. F.

Gravesend,
_September 21, 1909_.