New-York tribune., 1916-07-14

studies have failed to confirm the ear
lier ones. Moreover, experimentally
inoculated monkeys differ in one way
from human beings suffering from IN
fantile paralysis, for while the virus
NAV appear in the blood of the former,
il has never been detected in the blood
of the latter. The ordinary or domes-
tic fy may become contaminated with
the virus contained in the secretions
of the body and serve as the agent OF
its transportation to persons and to
food with which they come into con-
tact. Domestic flies experimentaliy
contaminated with the virus remain IN
fective for forty-eight hours or longer.
While our present knowledge excludes
insects from being active agents IN the
dissemination of infantile paralysis,
they nevertheless fall under suspicion
as being potential mechanical carriers
of the virus of that disease.
The attention which the recent epi-
demic of infantile paralysis has drawn
TO the diseases attended by paralysis
has led to the discovery that domestic
animals and pets are subject TO par
alytic diseases. The animals which
have especially come under suspicion
as possibly distributing the germ of in
fantile paralysis are poultry, pigs and
dogs and cats. But in isolated in
stances. sheep, cattle and even horses
have been suspected. All these kinds
of animals are subject to diseases IN
which paralysis Of the legs and other
parts of the body sometimes appears.
In not a few instances paralytlc dis
eases among poultry or pigs have been
noted to coincide with the appearance
OF cases of infantile paralysis on a
farm or in a community. Experimental
studies have, however, excluded the
above mentioned animals from being
carriers of the virus of infantile pa
ralysis. The paralytic diseases which
they suffer have long been known and
are quite different from infantile pa
ralysis. Their occurrence may be coin.
cidental; in no instance Investigated
has one been found to be responsible
for the other.
Routes Of Travel.
Studies carried out in various coun-
tries in which infantile paralysis has
been epidemic all indicate that, In ex-
tending from place to place or point
to point, the route taken is that OF
ordinary travel. This is equally true
whether the route is by water or land,
along simple highway or the line of
a railroad. In other words, the evl-
dence derived from this class of stud
les confirms the evidence obtained from
other sources in connecting the dis
tributing agency intimately with hu-
man beings and their activities.
The virus of infantile paralysis is
destroyed in the interior of the body
more quickly and completely than, in
some instances, in the mucous mem
brane of the nose and throat. 1t has
been found in monkeys, in which accu-
rate experiments can be carried out
that the virus may disappear from the
brain and spinal cord within few days
to three weeks after the appearance
of the paralysis, while at the same
time it is still present upon the mu-
cous membranes mentioned. The long
est period after incubation in which
the virus has been detected in the
mucous membrane Of the nose and
throat of monkeys is six months. 1t
is far more difficult to detect the
human than the monkey carriers of the
virus since, as directly obtained from
human beings, the virus displays low
degree Of infectivity for monkeys;
virus becomes incredibly active, so
that minute quantities are capable of
ready detection by incubation tests.
Yet in an undoubted instance OF the
human disease the virus was detected
in the mucous membrane of the throat
five months after its acute onset.
Hence, we possess conclusive evidence
of the occurrence of occasional chronic
human carriers of the virus of infan-
tile paralysis.
Fluctuation In Epidemics.
Not all epidemics of infantile paraly-
sis are equally severe. Indeed, great
variations or fluctuations are known to
occur not only in the number of cases,
but also in the death rate. The ex-
tremes are represented by the occa-
sional instances of infantile paralysis
known in every considerable commu-
nifty and from which no extension
takes place, and the instances in which
in few days or weeks the number of
cases rises by leaps and bounds into
the hundreds and the death rate
reaches 20 per cent or more of those
attacked. While all the factors which
determine this discrepancy are not
known, certain of them have become
apparent A factor Of high Importance
is the infective power or potency, or,
technically stated, the virulence, of
the micro-organism or virus causing
tn disease. This virus is subject to
fluctuations of intensity which can
best be illustrated by an example. The
virus as ordinarily present in human
beings even during severe epidemics
has low infective power for monkeys.
Bet by passing it from monkey to
monkey it tends to acquire, after a
variable number Of such passages, an
incredible activity. However, occa-
sional samples of the human virus re-
fuse to be thus intensified. But once
rendered highly potent, the virus may
be passed from monkey to monkey
through long but not indefinite series
Finally, in some samples of the virus
at least a reverse change takes place
the virus begins to lose its virulence
until it returns to the original or
even to a diminished degree of in
fective power. In this respect the be-
havior Of the virus corresponds to the
onset, rise and then the fall in num-
Der and severity of cases as observed
in the course of epidemics of infantile
paralysis and other epidemic diseases.
Hence either a new active specimen of
the virus may be introduced from with
out which, after certain number of
passages from person TO person, &C
quires a high potency; or a specimen
Of virus already present and left over
from previous epidemic after a rest
ing period and similar passages again
becomes active and reaches an infective
power which equals or even exceeds
that originally possessed. Another but
more indefinite factor relates to the
degree of susceptibility among chill
dren and others affected which at one
period may be greater or less than at
another.
Varying Individual Susceptibilities.
Not all children and relatively few