GENERAL PATHOLOGY

While pathology, in the correct and widest employment of the
term, includes practically everything concerning the study of disease,
by common sanction its meaning is considerably narrowed, and now
refers, in the main, to facts to be gleaned from microscopic and bac-
teriologic examination. To the knowledge thus gained, however, are
to be added other facts that throw any light upon the nature of the
disease and the morbid processes that characterize it, such as macro­
scopic features and mode of growth, character of the contained fluids,
as in vesicular, bullous, and similar diseases, examination of the urine,
etc. These all aid in a final conclusion. It is needless to say that the
study of pathologic anatomy must primarily be based upon a well-
grounded knowledge of normal histology. The feeling shared by many
students and physicians, judged by lack of interest, that in the study
of morbid structures and processes the pathologic anatomy of the skin
occupies an obscurely subservient position, scarcely to be considered
except by the dermatologic specialist, is one difficult to explain in view
of the knowledge that its investigation has disclosed. We have to do
with a structure subject to almost all the phenomena found in connec­
tion with internal organs—hyperemia, inflammation, hypertrophies,
atrophies, neoplasms, the character, behavior, and effects of micro-
organisms, etc, and that can be the more clearly studied, not only in
full development, but in various stages as well, and in tissues that are
obtainable during life, and therefore not subject to the changes and
consequent errors of observation and deduction necessarily connected
with the examination of tissue from the dead. A thorough study of the
commoner pathologic processes in this structure should not, therefore,
be left to the specialist alone; the teacher of pathology can find no tissue
so well adapted for the elucidation of the elementary and more import­
ant morbid changes to the student mind, and no structure whose careful
study of its various diseases will throw so much light upon the problems
of pathology in general. Indeed, in its general features cutaneous pathol­
ogy can scarcely be said to differ from that of other organs, although, as
would naturally be suspected, its nearest kin in this respect is that of the
neighboring stratified epithelial surfaces—such, for instance, as the
tongue.

The value of pathologic studies in cutaneous diseases, in adding
to our knowledge of the nature of the cutaneous malady, its anatomic
seat, the morbid changes, and its causes, has already been demon­
strated repeatedly. The significance of the grosser fungi and the small
micro-organisms has gradually been gaining greater and greater recog­
nition, and on these lines the clinician looks for future suggestions of

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GENERAL PATHOLOGY

increasing value for treatment, and also for the prevention of diseases
in which these organisms hold a pathogenic relationship.

Pathology and etiology are closely united, and one bears materially
upon the other, and their elucidation bears just as strongly upon the
subject of the therapeutic management. The various exciting and
contributory causes that give rise to the pathologic local alterations and
appearances have been referred to in etiology, and the initial step in the
local action leading to these changes may be in the vessels, nerves, rete,
upper part of the epidermis, the corium, especially the papillary layer,
in the glandular structures or the deeper tissues. The papillary layer
and the rete are important cutaneous structures, and their involvement,
either primarily or secondarily, a common occurrence in cutaneous
pathology, the latter the starting-point of epithelial new growths. The
hairs and nails are also sometimes the seat of certain changes. Not only,
however, may the disease take its origin in some particular division of the
skin, and from a particular constituent of this division, but also from a
special part of this constituent: it may be in the cells themselves, in their
protoplasm, in the interstitial tissue, fibrous tissue, elastic tissue, colla­
gen, muscular fibers, endothelium, or other component. The changes
may be simply congestive, inflammatory, atrophic, hypertrophic, neo-
plastic; show hyperemia, exudation, and infiltration, hyperplasia, with
new-tissue formation or degeneration. Depending upon its character,
seat, and limitations, it may appear merely as a diffused change, or it
may result in wheals, papules, vesicles, pustules, blebs, or destructive
alterations, often with secondary changes as a direct consequence of the
process itself, or partly or wholly from external or accidental factors.

The presence of micro-organisms, scantily or in numbers, in the in­
volved tissues of certain diseases can usually be readily demonstrated,
sometimes, however, requiring special preparation and staining and the
corroboration of culture experiments; the grosser parasites are easily
shown by moderate power, the lower organisms often requiring extremely
high magnification.

An attempt has been made in the following pages to present the chief
data and gross features concerning the pathology and pathologic anatomy,
somewhat briefly from necessity, but not to the extent, it is hoped, of the
omission of details for a proper comprehension of the essential characters.
The subject, however, in recent years has broadened to such an extent
that the writer of an average-sized volume on cutaneous medicine,
desirous of making it full in its practical working parts, can scarcely
present the histopathologic matter in the manner and to the extent that
might be wished, unless peculiarly gifted in the art of selecting the
essence from the mass of material and expressing it in terse, clear-cut,
but yet readily understandable, manner. The reader desirous, therefore,
of going further into this branch of the subject is referred to Unna’s
Treatise on the Histopathology, to Leloir and Vidal's Histologic Atlas,
and to Macleod’s recent handbook on the Pathology of the Skin and to
the various monographs referred to in the course of the text.

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