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Virulent Diseases.

| Cepuear News,
July 2, 1880.
tence of a true vaccine. I may even add that one or two
rials favour the idea that the attenuated virus keeps its
harader of mildness after passing through the bodies of
Juinea pigs, Will the same thing happen after repeated
sultivations and repeated inoculations? Only by experiments
 can such a question be answered.
At any rate, we now know of a disease caused by a
nicroscopic parasite, which may be obtained in such a
sondition that it does not recidivate, as other diseases
saused by similar parasites. Moreover, we have a variety
of its virus, which behaves towards it as vaccine towards
sariola,
The Academy may allow me a digression worthy of
attention. From what has been said, we can easily obtain
 chickens affeGted with the disease called chicken
:holera, in which death is not a necessary consequence of
‘he disease, We may then witness as many cases of cure
\s we may wish. Now, I do not believe that experimental
surgery has ever met with more curious phenomena than
‘hose which are present when the animal returns to health,
after inoculations have been made in the large pectoral
muscles. The germ of the disease multiplies in the substance
 of the muscle as it would in a vessel. Atthe same
ime the muscle swells, hardens, and becomes bleached at
:he surface and below the surface. It becomes filled with
rlobules of pus, but does not suppurate, Its histological
:lements are easily torn, because the parasitical germ is
scattered through them in numerous pockets, and it feeds
n a portion of their substance. I will, later on, exhibit
soloured figures showing the disorders caused by the parasitical
 germ in case of cure. The parasite is gradually
wrested in its development and disappears, while, at the
ame time, the portion of muscle which has been attacked
nites, hardens, and lodges itself in a cavity whose surace
 resembles that of a healthy granulating wound. The
portion which has suffered from the disease finally forms
i sequestrum, and is so well isolated in the cavity that
J0lds it that it may be felt by the finger under the skin,
ind, by the least incision, it may be seized with forceps
ind extra&ed. The small wound left in the skin heals
mmediately, and the cavity is gradually filled by the re-1ewed
 elements of the muscle. I will now place some of
:hese demonstrations before the Academy.
I have now to close by an explanation relating to the
10n-recidivation of the disease which occupies our attenjon.
 Let us take a chicken thoroughly vaccinated by one
>r more previous inoculations of the enfeebled virus. What
vill happen if we inoculate the same chicken again ? The
ocal lesion will be insignificant, while the first inoculaions,
 and, in particular, the very first, had been the cause
of such marked change in the muscle, that a large seques-.rum
 can be easily felt by the touch. The cause of the
lifference in the effects of these inoculations is to be found
antirely in a greater relative facility of the development of
.he germ of the disease at the first inoculations, and, in
‘he last inoculation, in the development being either
:ntirely wanting or very feeble and promptly stopped.
The consequence of this seems evident, and it is that the
nuscle, which has been seriously diseased, has become,
aven after it has been cured, unfit for the cultivation of the
zerm of the disease, as if this germ, by a preceding cultivation,
 had suppressed some principle which life does not
bring back, and whose absence prevents the development
of the microscopic organism. I have no doubt that this
axplanation, to which we are led by palpable fads in this
>ase, will be found to be generally applicable to all viruent
 diseases.
It must appear superfluous to point out the principal
-onsequences of the facts which I have had the honour to
sresent before this Academy. There are, however, two of
hese which may be mentioned. One is, that we may
10pe to obtain artificial cultivations of every virus, and
he other is, the idea of obtaining vaccines of the virulent
liseases which afili& humanity, and which are the greatest
Jdague of agriculture in the breeding of domestic
inimals.

twenty of them with the very virulent virus, these twenty
will die. If we inoculate the other twenty with attenuated
virus, these will all be ill, but they will not die. We let
the twenty chickens be entirely cured, and then if we
inoculate them with the very infeious virus, they will
not die. ‘The conclusion from this is evident, The
disease is its own preventive. It has the chara&er of
virulent disease, which do not recidivate.
Let us not be astonished at the singularity of this result.
 All things are not here as new as they appear at
first. In one important particular, however, there is a
10velty which will be pointed out. Before the time of
Jenner, who himself practised this method, as I have
already mentioned, there was a practice of inoculating
variola to preserve from variola, In our day, sheep are
noculated with murrain to preserve them from murrain,
and cattle are inoculated with peripneumonia to preserve
from this fearful discease. Chicken cholera shows us an
immunity of the same kind. It is an interesting fa&, but
it does not show any theoretical novelty. There is, how.
ever, an important novelty in the preceding observations,
a novelty which gives food for refle&ion on the nature of
virus. It consists in this, that we have here a disease
whose virulent cause is a microscopic parasite, which may
be cultivated outside of the animal economy, The virus
of variola, the virus of vaccine, those of glanders, syphilis,
the plague, &c., are unknown in their nature. .
This new virus is a living organism, and the disease to
which it gives rise has one thing in common with virulent
liseases, properly so-called, a quality heretofore unknown
in virulent diseases, caused by microscopic parasites: it is
that it does not recidivate,
The existence of this disease is a conneé&ing link between
 virulent diseases caused by a living virus, and other
diseases, in the virus of which life has never been
recognised.
I would not have it believed that the fa@s present the
constancy and mathematical regularity which I have mentioned.
 To believe this would be to ignore the great
variability in the constitution of animals, taken at hap
hazard from among domestic animals, and also the variability
 in the manifestations of life in general. The very
virulent virus of chicken cholera does not always kill
twenty times in twenty. Sometimes this virus only kills
eighteen times in twenty, but generally twenty times in
twenty. We may also remark that the virus, when re-Juced
 in virulence, does not save life twenty times in
twenty. Sometimes this happens only eighteen times in
twenty, and even sixteen in twenty. Neither is it an
absolute preservative by one inoculation. We may more
surely prevent recidivation by two than by one inoculation,
If we compare the results above stated with what is
known of vaccine and its relations to variola, we may see
that the less vigorous organism which does not cause
death, is analogous to a vaccine, relatively to the one that
kills, for it gives rise to a disease which may be called
nild, as it does not cause death, and, at the same time, it
preserves from the disease in its most deadly shape.
What other condition must this organism fulfil to be a
true vaccine like that of cow-pox? This condition is
that it should be a definite variety, and that we should
not be obliged to prepare it de novo, when we wish to use
it. We find here the same difficulty which presented
itself to Jenner. After he had demonstrated that inoculated
 cow-pox is a preservative against variola, he thought
that it was necessary to start from the cow-pox of a cow.
Jenner soon discovered, however, that be could get along
without cows, and make vaccine pass from one arm to
another. We may try to do the same by causing our
germ to pass from one cultivation to another. Under
:hese circumstances, will the germ begome a&ively virulent
or will it remain moderately so? Although this may appear
 very astonishing, I can say that the last supposition
is the correct one. The virulence of the germ, in the
small number of cultivations which I have attempted, has
not increased, and everything seems to point to the exis-