2
'' The one common property of the acute specific diseases is that they are all conta-
gious, that is, from some part of the sick something is given off which can, when properly-
applied, excite the same disease in another, and which can excite no other disease. Little is
known of what this something is ; and yet it is most important for the prevention and even for
the treatment of these diseases that we should know. Little is known of those conditions
of the system which render this something sufficient to the production of the disease in one
person while in another it is inert. For example, at a certain time one of these diseases is what
is called epidemic ; scarcely a person who has not had it and is exposed to the emanations
of the sick escapes taking it. On another occasion the disease is not epidemic and then many,
with equal degrees of exposure, escape.—Sir W. Jenner."
" The contagion therefore of ' this acute specific disease is something that is alive,
something which exhibits the phenomena of growth and self-propagation; and the doctrine
of a contagium vivum has been proven to be undoubtedly true as regards some contagious
fevers. ' In an argument of this kind it is of capital importance to get hold of an authentic
instance, because it is more than probable, looking to the general analogy between them,
that all infectious diseases conform in some fashion to one fundamental type. If septic
bacteria are the cause of -septicaamia, if the spirilla are the cause of relapsing fever, if the
Bacillus Anthracis is the cause of splenic fever, the inference is almost irresistible that other
analogous organisms are the cause of other infectious inflammations and of other specific
fevers.'—Professor William Roberts."
" In regard to vaccinia, small-pox, sheep-pox, diphtheria, erysipelas and glanders, the
virus of these diseases, it is believed, has been proved to consist of minute particles having
the character of micrococci, and that in regard to typhus, scarlet fever, measles and the rest
of the contagious diseases their connection with pathogenetic organisms is as yet a matter of
mere inference.—Professor William Roberts."
" Etiologists and pathologists have agreed to recognize one active principle which has
essentially to do with the cause of propagation of disease, termed provisionally contagium
or virus, which is believed to be contained in the secretions of the affected person. Beale's
description of its material substance is the following:—
" The minute contagious bioplast is less than the /ill/ of an inch in diameter and often
100,000
so very clear and structureless as to be scarcely distinguishable from the fluid in which it is
suspended. Such a minute particle may readily be transferred from the affected organism
to an apparently sound organism. It may be carried a considerable distance from its source
without losing its marvellous power of causing in the organism invaded a series of changes
resembling, and often in every minute particular, the phenomena which have occurred in the
organism from which it was derived. And it is established that there exist different kinds
of contagious living bioplasts, each capable of occasioning specific phenomena which
distinguish it. The poison of small-pox will produce small-pox, not typhus fever, or
measles, &c.; nor will any of these produce small-pox. Without, therefore, pretending to
identify the actual particles of the living bioplasm of any contagious disease, or to be able to
distinguish it positively from other forms of bioplasm, healthy and morbid, present in the
fluids on the different free surfaces, and in the tissues in such vast numbers, I think the
facts and arguments I have advanced prove (1) that the contagious, virus is living and
growing matter; (2) that the particles are not directly descended from any form of germinal
matter or bioplasm of the organism of the infected animal, but they have resulted from the
multiplication of particles introduced from without; (3) that it is capable of multiplying and
growing in the blood; (4) that the particles are so minute that they readily pass through the
walls of the capillaries and multiply freely in the intestines between the tissue elements or
epithelial cells; and, lastly, that these particles are capable of living under very different
conditions; that they live and grow at the expense of different tissue elements and retain their
vitality although the germinal matter of the normal textures, after growing and multiplying
to a great extent, has ceased to exist.—Beale on Disease Germs."
Some pathologists contend that infectious diseases depend on bacteria; but
although there is no doubt that they are found in the blood in many fevers, yet
that they are the causative agents of disease is said by others to be open to the
gravest doubt. Dr. Lewis' researches 011 this question, published in the Report
of the Sanitary Commissioner with the Government of India for 1877, are very
important, and are described by Dr. Ouningham as " a valuable contribution
to the literature of the obscure subject of the origin of epidemic diseases." He
arrives at the conclusion that these microscopic organisms have no specific action
in the causation of. disease but are rather to be regarded as epiphenomena.
Enteric fever is not believed to be contagious in the, sense that small-pox is,
and it is stated that there is little danger in admitting patients suffering from this
disease into the wards of a general hospital. The morbific contagium is supposed
to be contained in the stools of the patient, and Aitken says :—" These dischar-
ges drying up the germs of the disease are thus preserved as effectually as the
crusts of small-pox preserve the virus of that disease ". In this way, according
to those who believe in the specific contagium theory, the disease is spread; for, as