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What the Rockefeller InstituteHasFound Out About Inf antile Paralysis
Dr. Simon Flexner, Director of the Laboratory, Announces That the Baffling Disease
Travels Up Into the Brain Through the Nerves of Smell in the Nose, and That the it- ■ ■ ,
Germ Is too Minute for the Most Powerful Microscope to Find, and Can
Make Its Way Through the Walls of the Finest Filter. 1
Hy Prof. SIMON FLEXNER, M. 1),, After Effects of the Disease. I ||l
Director of the Laboratories of the Rockefeller Institute for Medical Research, N.Y re ' - 11!
ilt« following tx taken from Profrnsor
’7< ’nrr'v rer.n/ address before the Charing
<'rnsx Hospital. London.)
EPIDEMIC poliomyelitis (Infantile pal
i ,ysi. i is, pre-eminently a disease of
• i\ <-!n)dh>. I and finds the highest
ei.eii age of its victims In the first five
years of 'll'.- nut does not wholly spare
eider ' Iren or eVen adults. It is admit
le i , h/o . non-, and while it is true that
many ic..ie instances of single than of
~u ijple < iims oeeur, .vet multiple ones, are
' 'i;> rir means rare. The period of great
in e is during the months of Au
gi. Sep;, ii.aer ami October in the northern
urn ,1' and the corresponding months
In in hemisphere, but. the epi
'. 'iii i■ ; iii> in the early Spring and Sum
. u. sit - and the disease does not
. . ppi ar during the Winter
It does md, therefore, necessarily
;• .d any period of tile year.
It" i.i'. n -.w been able to arrive at sev
. i i: ; riant n on*-luslons. The monkey
u.ido r< iii.iriy to develop an ex
agreeing in all essen
wit poliomyelitis in man.
iii' . ithm is necessary, since keeping
ind paralyzed monkeys together
J"i 'i to infection. The parasitic
"I the disease can traverse the blood,
it) 1 nioni ey, to reach the central ner
vous organs but will, difficulty, while it
•-I 1 \ ; m iso- lhe peripheral (superficial)
nerve.> I hat the natural spontaneous dis-
so .-ailed In man am' the induced
di- in monkeys are very alike is fur
how |,y microscopic study of the
spinal ord and brain, which exhibit
changes ihal are identical.
The pathological effects are of two kinds:
’ 11 •" nerve cells, not in the anterior
gray matter alone, but in the posterior
matter ot the spinal cord ami in the
intervertebral ganglia (nerve centres in
the spinal eord), medulla (top of the spinal
cortb and brain: and cellular invasion of
the pia arm huoldnl membrane (the wob
llke envelope that covers tile brain and
spinal cord) of the spinal cord and medulla
that follow the blood vessels into these
parts „m| puss into the adjacent gray and
whiti matter.
I hr- altered vessels permit an escape of
albuminous fluid and blood cells into the
meshes of the membrane, where they mingle
with the cerebrospinal liquid .(fluid sur
rounding the brain and spiral cord) and
into the spaces in the tissue comimsing the
solid white and gray nutter. Sometimes
the nerve cells, sometimes the meninges
(the different coverings of the brain and
spinal cord) vessels and supporting tissues
suffe most When the nerve cells arc 1 ex
tensive]?- injured the paralysis is marked
wi en (he meninges are much affected the
svmplonis are like those of meningitis
I ; ■ virus of poliomyelitis displays a high
Hftmity f.„- nervous tissues, but’it Is the
wile involvement of (he nutritive vascular
• ii .th* pathologlenl process that sub-
Jit* sensitive nerve ceHs to ho high
1 ute <<i injury and < lest ruction.
The Infectious Agent of Poliomyelitis
The microscopical conditions we ob
served tn the course of our
were suggestive of two things: first, the
Vulture f the parasite itself; and secondly,
he process of generation of the effects or
•-mils t icinselves. Ip t o this time no defi
nite ir isiie could be detected in the ner
vous tissues either in human beings or
monkeys, u»r was anything of the kind
found m the blood of other organs. The
s> unity oi polynuclear leucocytes (white
blood corpuscles with many centres) in th. 1
<ord its. ■ - pok. against a simple bacterial
altered cerebrospinal liquid and spinal
parasite lhe 'urge number of mononuclear
<■ Is spoke either for a protozoal (animal)
1 'o'.isii. Nerdier could be found, although
I " mo-- ailed methods of staining and
cultiv.it ion were employed.
There remained the possibility ~f tin
p irasite heir.; invisible or ultra-micro
s 'p: ' and Ii terabl. This it proved to be
f.e- when a portion of the spinal eord of a
i -ciitiy paralyzed monkey was made into
an emulsion with sterile distilled water or
simp:, saline solution and then ceqtrifuged
to remove the coarse suspended matter
mid afterwards pressed through a Berke
fe earthenware filter —which excludes or
binary cells, bacteria and protozoa -the
...a. i'tuid resulting was still capable of
: i .insm:tting the disease.
Tile i ivity of the filtrate is very great,
sc. i fraetio'n of a thimbleful still suf
ues . cause paralysis and death. The
. distinction to be noted between the
. : i c corresponding amounts of the
ei.iui'ioii and tillered lluid is that the form
al . .•» aior. quickly. as would be expected
ii.'ii'. the fa.-t that it contains a greater
i .; ■ the invisible organisms. Thi'
o . : .- i- -on comp-nsated by the mul
ti; i .-'a o: d.ose iii t!m tiltrate, so thiv
the ci. i r.-suit is the same.
in i-i.deavo|-jug to trace the channel of
i .; the virus inn. the body certain
t ; : 1.-.’ "dll its distribution in the body
>.n- . ■ r.s , pit u... ..-a ami considered.
I .- iutectious agent ..f poliomyelitis nt
a- .. . uiedy the central nervous system
Hi i. d. it hi. - i.evn detected regularly in
■■ oil . rd and brain, and In the me
s.n;. I- ymph nodes (coagulated particles
el 'tn;, i in tin- alslomimil walls) among
a. . in'crnii) organs. It Ims also been
i in the mucous membrane of the
and throat, and in the mucus
ns of this membrane, and in the
■etioiis of the stomach, and the
large intestine. The virus Ims
.'.'ted in sui-ii important organs
. . ii. kidneys, liver, or bone mar
I i ,s gnifi .-.nt, but in at
" an- should be
■:- ii si ..> .<• that at presen
-m.- n ■ 111, only of detecting th
■ - i. it. its to mon
keys, in which it produces characteristic
paralysis and anatomical changes.
On this account small quantities of the
virus may conceivably escape discovery.
However, the conclusion is none the less
inevitable that detectable amounts of the
poliomyelitic virus exist, only in the few
situations ami organs mentioned. The dis
tribution of the virus is identical in human
beings, tile subjects of the so-called spon
taneous poliomyelitis, and in monkeys, in
which the experimental affection is pro
duced. Nor does it. matter how the experi
mental inoculation is accomplished, and
whether the virus is Introduced by injection
into the brain or large nerves or subcu
taneous tissue or peritoneum, or whether it
is merely applied to the nasal mucous mem
brane which it should be emphasized, next
to direct intracerebral injection, affords
the surest means of causing the experimen
tal disease. In whatever way tile infection
is produced purposely, the distribution of
the virus in infected monkeys is the same
as in infected human beings.
Ihe virus is one that is not known to
increase aside from the infected body,
and hence in order that it shall be cap
able of |ir<>|>agating poliomyelitis it must
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A Spinal Nerve Certtre, Showing a Diff use Inflammatory
Process and Beginning Death ok Nerve Cells. :
W ’■ i -' 1 '
ere the
I.®.- virus distrlb-
/ i ■ uted by the
-"" ■■ blood the me-
Diagram Showing Channel by Which the Infantile fV."” « h n 1n n 1
Paralysis Germ Reaches the Spine. A. Nerves of ( . nr d) spin
Smell in the Nose, Along Which the Germ Travels. al cord would
B. Olfactory Lobe or Centre of Smell in Brain. C. have become
Head of Spinal Column, Which the Germ Reaches infective rather
by Way of the Olfactory Lobe. t cTr y Vo b eT.
secure a means of escape from the infected
animal. The escape is now known to occur i
alon» with the secretions of the nose and
throat ami the discharges from the intes
tine. x
It Is known that in monkeys the virus
is incapable of passing the barrier of the
unbroken or slightly abraded skin, of be
ing taken up from the stomach or intes
tine unless the functions of these organs
are previously disturbed ami arrested by
opium. and it Is further known that it
traverses with difficulty, or even not at all,
the substance of the lungs. On the other
hand, it is established that the virus passes
with readiness and constancy from the in
tact, or practically intact, mucous mem
brane of the nose to the central nervous
system.
To illustrate this point I wish to de
scribe briefly an experiment. The spinal
cord of a paralyzed monkey always con
tains the virus we are considering. If a
camel's hair (lendl or pledget of cotton *■»
covered with some of the broken up tissue
of such a cord and painted upon the mucous
membrane or rhesus monkeys these ani
lmils will develop in due time the paralysis
ami other symptoms of poliomyelitis.
Hence the virus enters the body from this
surface, even though no gross Injury has
been Inflicted upon the membrane
How the Virus Goes to the Brain.
We should now ask ourselves if the virus
actually ascends to the brain by the direct
path of the olfacte-y nerves (nerves of
smell) or indirectly after first entering the
blood. This Is the same question that has
been buffeted about in regard to epidemic
meningitis. The meningococcus i germ of
meningitis) Is found in the nasal mucus
of persons in contact with eases of men
membrane of rhesus monkeys these ani
ingitis and in the sick themselves. Opin
is divided as to whether they go at once
to the membranes of the brain or tirsi
penetrate into the blood.
To produce meningitis in monkeys it
does not suffice to inoculate the nasal mem
brane; the meningococci must be injected
into the meninges themselves. But so in
oculated they escai>e in part along the
nerves of smell into the nose The virus
of poliomyelitis Is so active that implanta
tion in the nose does not suiffee to cause
infection. If a monkey is sacrificed about
forty-eight hours after an intranasal inoeii
lation and the brain and spina! cord are
removed and then the olfactory lobes, (cen
tre of smell in the brain) portions of the
medulla and spinal cord are separately in
ocnlated into other monkeys, infection Is
produced by the olfactory lobes alone, si o
in this brief period the virus b.is not ye'
reached oilier and more list.in parts at
<Uu ueiwus organs.
■ w-yn, Is; “• B-v O
fe- WiA # \ i I & i F- < ■'>
*, • i . J J I ' ■-/ .
f a J .
' ' 'of ' y
• Y Simon Flexner, Director „f „
Laboratories of the Rockefeller ! n .
r ;s , , stitute for Medical Research, N Y
1 " * •■— ■ ■ r>"
~ ~~ y
since they exhibit a greater selective affin
ity for the parasite. The conclusion is un
avoidable that the virus ascends by the
nerves of smell to the brain, multiplies
first in and about the olfactory lobes, and
in time passes, as I believe into the
cerebro-spinal liquid, (fluid between the
coverings of the brain and spinal cord I
which carries It to all parts of the nerv
ous organs. . .
Wo have already learned that the virus
can pas*-* along a large nerve, such as the
sciatic, which carries it first to the lumbar
cord, (lower part of spinal cord) whence it
ascends to higher levels; we need not.
therefore, be astonished to find that it can
wander along the olfactory nerves and then
descend to lower levels. The large peri
pheral nerves are prevented anatomically
from becoming infected in nature, while
the small olfactory (filaments are advan
tageously placed to act as the means of
transportation.
Hence the view I desire to place before
you: that the nasal mucous membrane is
the site bqth of ingress and egress of the
virus of |H>liomyelitis in man. Support for
this view is found also in the study of the
microscopic changes in the meninges ami
tin* central nervous tissues. Since the virus
survives in the dried state It may be car
ried in dust; and In one instance it has
been detected in sweepings from the room
occupied by a j>erson ill with poliomyelitis.
Its distribution ns spray in coughing ami
spe iking is readily accomplished, and by
this means both active cases and passive
< arriers may conceivably be produced.
Still one link in the chain of causation
of poliomyelitis as here outlined remained
to be forged. The clinical evidence is
strong in the suggestion that human car
riers of the poliomyelitic virus exists. The
virus has now b<*en detectisi In the secre
tions of the nose, throat and intestines of
la-rsons suffering from abortive or ambu
lant attacks of poliomyelitis. The unrec
ognized examples of the abortive disease
play a highly important part in the dissem
ination of the virus, through which the
area of infection is extended, and the num
ber of the attacked increased.
A similar part has been accorded by
clinical observation to the healthy virus
carrier, and the healthy carrier is the
last to be detected, and Ids existence con
firmed experimentally. The obstacles in
the way of this confirmation are consid
erable, but not insuperable. It is to be
remembered that we jtossess no means of
ch, .v. ring the virus except that of animal
inoculation. Should the experimental re
sults arising ft*, nt the inoculation of tne
secretions of the nose and throat of such
healthy carriers Ih> confirmed the evidence
for the mod* • infection as hero out
im-d w*'>ild lie complete. The membrat'
of the m*se and throat is far more vulner
able m young individuals, wheucv arise.;
the greater prevalence during childhood
of those diseases the causes of which seek
this avenue of entrance into the hotly
Among them are included diphtheria,
measles, scarlet fever and meningitis.
Would the establishment of the respira
tory avenue of entrance of the virus ex
clude all other modes of possible infection?
By no means. Plague bacilli are known
to be Inoculated Into man by rat fleas; bitt,
the pneumonic form of the plague is ad
mittedly caused by respiratory inoculation
Diphtheria arises upon the mucous mem
brane of the throat, but can develop in a
wound of the skin; the virus of smallpox
enters byway of the throat and nose, but
can enter by a skin abrasion; the virus of
foot and mouth disease. Is taken in with
food, hut produces infection when injected
into the skin. Hence at the moment, while
knowledge is still recent and not yet per
fect. lite too absolute adherence to one
point of view is to be avoided.
1 Indeed, the propondetance of cases in
the late Sumi»’r and Autumn months early
suggested an insect carrier of the infec
tion. House flies can act as passive con
taminators, since the virus survives upon
the body and within the gullet of these in
sects.
Hens May Be Disease Carriers.
The frequent prevalence of epidemics in
sparsely populated country districts has
led, moreover, to consideration of domestic
, animals as sources of the infection.
Paralysis of dogs, horses, pigs and fowl
has been observed not uncommonly, but
' thus far without clear correlation with
paralysis in man. Perhaps the most fre
quently observed coincidental paralytic.dis
i eases have been between hens and human
beings. .
We have, happily, made some progress
I in a method of direct, local treatment by
Injections that have given excellent re
sults in meningitis.
Remote as some of them may <eem, the
i considerations to which I have called your
I attention have a bearing more or less vital
upon the problem of a specific and effective
treatment of poliomyelitis.
Poliomyelitis is not a disease with a
very high mortality; its chief terror lies
’ in its appalling power to produce deformi
ties. When death does occur it is not the
result, as in many infections, of a process
* of poisoning that robs the patient of
strength and consciousness before its im-
' minenee. but is caused solely by paralysis
of the respiratory function, sometimes witli
merciful suddenness, but often with pain
till slowness, without in any degree ob
scuring the consciousness of the suffocating
victim until just before the end is reached.
No more terrible tragedy can l>c witnessed
The employment for treatment of the
immune serum, taken from monkeys or
* from human beings, exercises a definite if
not very strong protective action gpon in
oculated monkeys. Either the disease is
prevented altogether or’ its evolution is
1 modified in such a manner as to diminish
its severity. When the virus used for ii
* octtlation is highly adapted to the monkey,
and thus very virulent, it is more difficult
to control the result than when ii departs
less from th*: ?rigiual human typo and t
less active
The immune serum has thus
far acted best when it’was in
jected into the subdural space
on several successive days.
4<-, <•» nAnfiimnlt v ti-it It F 11. .
This Is in conformity with th
z fact that, however introduced
into the body, the virus establishes itself
in communication with the cerebro-spinal
liquid, where it propagates for a time.
After a time the virus localizes in
the nervous tissue itself, and becomes
accessible not only from this liquid,
but probably from the general blood
; also. The serum introduced into the
subdural (under the outermost covering of
; the brain) space soon escapes into the
f blood; and thus a double action is secured,
i On the one hand it reaches the nervous
[ tissue directly from the cerebro-spinal
, liquid, and on the other with the blood
An immune horse serum at first gave dis
. appointing results, but latterly its employ
meat by intramuscular injection has given
more promise. But none of the sera men
, Honed*can be regarded as having more
than touched the fringe of the problem of
a cure for the disease.
Such brilliant success has been rei.ntly
recorded in respect to the specific chemical
therapeutics of infection that an effort has
been, and still is being, made to attack the
problem from tais quarter. Here, also,
, only a starting point has been secured and
the subject merely opened to'further ex
' perimentation. The point of departure
t which we have adopted is the drug hex
amethylenamine (urotropine), which pos
! sesses a degree of antiseptic, action in flic
body and is known to be secreted in the
cerebro-spinal liquid. When the drug is
1 administered by’ mouth it can be detected
by chemical tests in the liquid in a short
time. When i •illation of virus and ad
ministration of the drug are begun to
-1 gether and the administration continue*!
lor some days afterwards tin* development
of the paralysis is sometimes but not al
ways averted.
Hexamethylenamine lends itself to modi
fications by the addition of still other anti
septic groups to its molecule. We have
tested a large number of such modifica
tions and have found certain lines to ex
' ceed the original compound in protective
power, and others to promote the onset of
paralysis. This is the common story of
’ drugs. None are without wholly some d*
gree of injurious action upot the sensitive
and vita! organs of the body. But manipu
’ lative skill has already succeeded in elirn-
L imiting the objectionable and improving
the valuable features of drugs so that they
' exert their action but little upon the organs
1 and severely upon the parasites when they
become useful as therapeutic agents
The House Fly Conveys Infection.
Since Dr. Flexners address further re
searches by the Rockefeller Institute ex
perts seem to have definitely proved that
the common housefly is the main source of
infantile paralysis infection.
Drs. ('. W. Howard and Paul F. Clark
experimented with flies, mosquitoes, lice
and bedbugs. Wit it the exception of the
1 mosquitoes, the insects were permitted to
teed on a portion of a spinal cord taken
from a monkey which died of the disease.
Mosquitoes fed upon figs, which had been
* injected with a mixture of blood ami in
fected spinal matter.
All the insects ittr-i t<'..-l > g w*-i- killed
Little Convalescent Trying to Walk with
Specially Constructed Chair.
w ith el her, ground up with sand and sail
solution and passed through a Berkefeld
filter. The filtrate was infected, in the
manner described by Dr. Flexner, into th«
brain of the Rhesus monkeys.
The flies were the ordinary species ot
housefly, bred in the laboratory. Every
monkey infected with the filtrate from
their bodies died from infantile paralysis.
No monkey inoculated with the filtrates
from mosquitoes or lice showed a trace
of infection. One monkey out of sixteen in
oculated with the bedbug filtrate showed
the characteristic symptoms of poliomye
litis.
Tite lieduct ions from these experiineu s
says the experts’ report, are clear. The
domestic fly may become contaminated
with the poliomyelitic virus which it may
obtain in nature from infected discharges
from the noseband throat or intestine. He
cause of the resistance of the virus to
ordinary physical changes, especially when
combined with mucous secretions, it can
be transported in a living state on the sur
face of tlwir bodies for two or more days
and because of the resistance it display;
to digestive secretions, within the eso
phagus and stomach for at least several
hours. The survival in the gullet permits
of the contamination of objects during tiie
feeding process through the act of re
gurgitation which the fly performs in
moistening and dissolving its food.
The flight of the house fly is consider
able. Copeman, Howlett ami Merriman
found marked flies one-half to three-quar
ters of a mile from the (dace of their libera
lion. On this account these potential pas
sive contaminators are theoretically <apa
hie of carrying and depositing the virus at
a considerable distance from the point at
which the original contamination occurred.
I hrough the ordinary active habits of the
fly the virus may be transferred to persons
or to tilings with which persons com* D.o
* lose relation, and by the death of the flies
they may through disintegration liberate
surviving virus: that may possibly be con
verted into dust. The finding of the '
hi the sceretions of the nose, throat. ‘ '*
gastro-intestinal tract of human beings
suggests that through the agency of •■■ ■
a passive eontaminator as the fly, the Dru.-
may be taken into tne bodies ot liui '.*
b*ings in which, conditions favoring,
may develop and cause infection.
The conclusions of the experts are:
“ Fhe domestic fly (J/usca ilomi'ttii fi) cm
< arry the virus of poliomyelitis in an
five state for several days upon the sir. .
of the body : nd foi several in urs within n
east to intestinal tract.
'.Mosquitoes tCule.r pipicni Cuhi * 1
I'itmis, and ( tilc.r rnntator) in our experi
i.ients, nave not taken up and nmintai 1
in a living state the virus from the spina
cord of monkeys
“Lice (P< rliculitx capitis and Pcdt i 1
have not taken the vim
of the blood of monkeys or maintain
in it living slate.
‘■rhe bedbug fCinie® Icctulai ui
taken the vires with the blood from
■*■'•*-d monkeys ami urnintaine*! i' ib
nig state within the body foi * p’ l
seven days/’