nious devices and by skillful manipulations,
is as fascinating as any tale of adventure.

When the microscope began its work, how discouraging was the vastness
and complexity of the discoveries which it brought to light; how many
years has it been diligently used, and how uncertain are we still
about many of its revelations! But what a happy conjecture of man, and
as proper environment takes place we may reach better results! Let me
give an illustration:

Some thirty years ago, Virchow began his studies and lectures upon
cellular pathology. The enthusiasm which he awakened spread over the
whole medical world. The wonderful attention to detail, the broad
philosophy which signalized his observations, were alike remarkable.
His class room was packed with students from every country, who
thought it no hardship to struggle for a seat at eight o'clock in the
morning. With his blackboard behind him and specimens of pathology
before him, and microscopes coursing upon railway tracks around the
tables which filled the room, he was the embodiment of the teacher;
his highest honor was as discoverer. The life and importance of the
cell, both in health and disease, it has been his work to discover and
to teach. The point of view from which he has classified tumors is
founded on this basis, and remains the accepted method. The light
which he cast upon the nature of inflammation has not yet been
obscured, and while other phenomena appear, the multiplication of
cells and nuclei and the formation of connective tissue in the process
of inflammation will always call to mind his labors.

To one of Virchow's pupils, Prof. Recklinghausen, we chiefly owe our
knowledge of the phenomena of diapedesis as a part of the inflammatory
activity. How incredible it seems that masses of living matter can
make their way through the walls of blood vessels which do not rupture
and which have no visible apertures!

Virchow fixed his attention upon the forms and activities of the
cells, their multiplication and degradation, and how they build up
tissues, both healthy and morbid.

To another matter with which, both literally and metaphorically, the
air is filled, we must also make allusion. The existence of
micro-organisms in countless numbers is no new fact, but the influence
they may exert over living tissues has only lately become the subject
of earnest attention. So long as they were not known to have any
practical bearing upon human welfare, they in