THE WORK OF THE SANITARY INSPECTORS
Each of the twenty-five districts into which the Zone was divided, as
far as the general sanitary work was concerned, was in the charge of
a sanitary inspector. The sanitary inspector had under him a force of
from twenty to one hundred laborers, with assistants and foremen as
necessary. The districts varied considerably in the number of people
living in them. Some of the districts had as many as eight or ten
thousand people; some only a few hundred. The area of the district
varied between fifteen and thirty-five square miles. The Zone extends
for five miles on each side of the Canal, that is, a strip ten miles
broad and fifty miles long. Most of the population was located on
each side of the Canal, within about a mile of its axis, while a few
houses and cabins were scattered through all parts of the Canal Zone.
Sanitary work, generally speaking, was done only within a mile or so
of the Canal itself. All brush and undergrowth were cleared within
two hundred yards of houses and villages, and the ground carefully
drained within the same area. There was no object in carrying
sanitary work beyond the populated area. Even if mosquitoes bred
where no human beings were living, no harm would be done, as there
would be no one to infect.
All told, the country under the jurisdiction of the Isthmian Canal
Commission amounted in area to about five hundred square miles, and
only a hundred of this was affected by the work of the Sanitary
Department. The great work of the sanitary inspector was his
anti-mosquito work. In the early days he paid most attention to the
stegomyia mosquito, but after the fall of 1905 when yellow fever had
been conquered, attention was concentrated on the anopheles, the
malarial mosquito.
For the elimination of the stegomyia, the inspector in these country
districts took the same measures as described in Colon and Panama
against these mosquitoes, though of course on a very much smaller
scale. Against malaria, he had a sufficient number of laborers under
one or more foremen, according to the size of the district, who cut
the brush and undergrowth within two hundred yards of all villages,
houses and dwellings, and who also cut the grass within this area
whenever it reached a foot in height. This was done for several
reasons. The adult mosquito is destroyed by wind or sunlight, and
he seeks all sorts of shrubbery, grass and foliage for protection
against both of these enemies. Therefore, if the brush, shrubbery
and high grass is cleared off within two hundred yards around a
dwelling, there is no shelter for the mosquito from either the wind
or sunlight, and there are therefore no mosquitoes within this area.
The anopheles, the malarial mosquito, is not a mosquito of strong
flight; two hundred yards is, in general, a good long flight for
her. If there were trees and shrubs and bushes every few yards,
the anopheles mosquito might travel very long distances and not be
much exposed to either the sun or the wind. But if an area of two
hundred yards around each building is kept clear, she will not often
be able to cross such a zone without destruction, either by sun or
wind. Clearing this zone exposes the ground to both sun and wind,
and by these forces alone many of the smaller pools will be dried
up and made unfit for mosquito breeding. I have often seen this
measure alone, that is, clearing the zone, cause a swampy place which
I had expected to have to drain, to become dry and cease to breed
mosquitoes.
[Illustration: Oilers at Work In Marsh.]
[Illustration: Burning Out Ditch With Oil Spray.]
It was also the inspector’s duty to see to the drainage. For this
purpose he had a properly trained body of men under his control.
The drainage was, of course, very much more extensive in area than
the grass and bush cutting, for not only had the cleared zone
itself to be drained, but all the area within that zone, and also
the water-courses leading off from the drained areas had to receive
attention. Many times we found that anopheles were breeding very much
beyond the two-hundred-yard limit and still coming into the village.
In one case we had a very large flight of anopheles which lasted for
two or three weeks, and they were found to be breeding more than a
mile from the village of Gatun. So, as a matter of fact, our work was
very many times carried beyond the two-hundred-yard zone.
The inspector used several methods of draining, being governed in his
choice by local conditions.
One of these methods was the open ditch, such as the farmer used
for the ordinary draining in agricultural work. At Panama, there
were several objections to this method. While the ditch drained the
surrounding ground and stopped mosquito-breeding at this point, it
became a most excellent breeding-place itself, as the grass grew in
the bed of the ditch. At Panama, rain fell daily for eight months of
the year, and the temperature was always high enough from one year’s
end to another to encourage vegetable growth. The grass, therefore,
grew so rapidly that the ditch had to be cleaned out every two or
three weeks. The cost of keeping open a surface drain of this kind we
found to be very high.
Another system of drainage which the inspectors used very freely and
found very useful, was that of filling the ditch, after it had been
excavated, with broken stone. This largely prevented the growing of
grass, and also prevented any development of mosquitoes in the ditch
itself. Another form much resorted to was that of lining the ditch
with concrete. This entirely prevented the growth of grass and did
away with the expense of up-keep. The only expense involved in caring
for such a ditch was that of a man going over it now and then and
removing such obstructions as may have gotten in. Mr. Le Prince and
his inspectors became very expert in this style of concrete work, and
finally, by the use of chicken wire as a framework for strengthening
the concrete, were enabled to lay a ditch of this type very cheaply.
Wherever the drainage was expected to be used for a year or more, we
found it more efficient and economical to use concrete rather than
the open ditch.
Mr. Le Prince and his staff devised several processes whereby the
cleaning of these ditches of grass was much cheapened. Several
solutions of arsenic were found which, when applied to the grass,
killed it. Such a process kept the grass down for a much longer time
than that of simply cutting it out with a hoe. A burner was devised
which atomized oil under air pressure, making a very hot flame which
destroyed the grass roots.
After once clearing a piece of ground the inspector had to keep
it in such condition that it would not protect adult mosquitoes.
He had, therefore, not only to keep it clear of brush, but also
must not allow the grass to grow more than a foot in height. For
grass-cutting, there was a great economy in using the horse-mower
wherever we could. Numerous open ditches interfered with the use
of a horse-mower. To meet this difficulty, the inspector used
sub-soil tiled drainage wherever it was feasible. This is the ideal
anti-mosquito drainage. It carries off the water, so that there is no
formation of breeding-places on the surface. After it is once laid
it requires no work or expense for up-keep, and a horse-mower can be
used just as freely over its surface as if there were no ditch there.
With the various methods just mentioned we drained pretty well about
one hundred square miles of territory, constructing in all some five
million feet of open ditch, some one and a half million feet of
concrete ditch, some one million feet of rock-filled ditch, and about
one million feet of sub-soil tile.
For doing this ditching, each inspector had a gang of men under a
competent foreman. In many instances, where the work was extensive
and required unusual skill, such as tile-laying, the gangs especially
experienced in this work were transferred from district to district.
Often it is not possible to drain—for instance, a large swamp area,
or where the locality is to be occupied so short a time that it is
not economical to drain. In such an extensive engineering work as
was being carried out on the Isthmus, the construction work was
constantly interfering with the drainage and making pools and puddles
which had to be looked after. In these instances, and many others of
similar character, the use of kerosine oil was our only resource. The
oil was distributed from a can on a man’s back, by a pump which he
worked with his hand, forcing the oil through a nozzle to the place
which he wished to affect. In general, we used crude oil of commerce,
not because it was the best, but because it was so cheap that we
could use it much more extensively than the rectified oil. It was so
thick, however, that we had to thin it with various mixtures before
we could spray it through the nozzle. This cost us a fraction over
two cents a gallon, and we used about fifty thousand gallons a month
over the hundred square miles of territory we were treating. It is
not necessary to look after all collections of water in order that
mosquito-breeding may be prevented. If the water is sufficiently deep
and clear of grass, so that the fish can have free access, these fish
will destroy all the larvæ, and mosquitoes will not develop. But all
natural collections of water in a warm climate such as Panama have
grass and algæ freely growing on its edges, and these obstructions
protect mosquito larvæ, particularly the larvæ of the malarial
mosquito, the anopheles.
Gatun Lake, the large lake made by the damming of the Chagres River,
gave us a great deal of trouble on this account during the last two
years of construction. Not only would the anopheles breed freely
around the edges of the lake, but wherever trees or vegetable matter
were floating, there algæ grew freely and anopheles larvæ were found
in abundance. We found that the anopheles larvæ on the Isthmus
developed just about as freely in the mountains as they did in the
lowlands. The clear mountain torrent seemed to be just as acceptable
a home for the anopheles as the edge of the lowland swamp. At Panama,
the temperature remains the same all the year round. The water of the
mountain stream is sufficiently warm for his development, just as in
the swamp. The stream, as it winds down the mountain, grows grass and
algæ freely on both sides of its tortuous course, and here the larvæ
of the anopheles find safe harbor. Into this grass and algæ oil will
not spread. We had to find something that would dissolve in the water
and poison the larvæ protected by the grass and algæ.
Dr. Samuel Darling, of the laboratory, finally worked out a mixture
of carbolic acid, resin and alkali, which would emulsify in water
and accomplish this purpose. The mixture was known as larvacide. The
method of its manufacture was as follows:
One hundred and fifty gallons of crude carbolic acid are heated in an
iron tank having a steam coil, with steam at fifty pounds pressure.
Two hundred pounds of finely crushed and sifted common resin are
dissolved in the heated acid, and thirty pounds of caustic soda
dissolved in six gallons of water are added. There is a mechanical
stirring rod attached to the tank. The product is ready in a few
minutes, yielding about three and one-half barrels.
COST OF MANUFACTURE, AUGUST, 1909.
_Amount manufactured: 14,600 gallons (292 barrels)_
12,600 gallons crude carbolic acid at 12 cents per gal. $1,512.00
12,300 pounds rosin at $2.48 per hundred 305.04
2,550 pounds caustic soda at $3.70 per hundred 94.35
2 tons coal at $5.00 per ton 10.00
Labor 94.46
Supervision. 50.00
————————
Total $2,065.85
Cost per gallon 14.14
To insure the manufacture of a uniform product, requisitions called
for crude carbolic acid of a specific gravity not greater than 0.97,
and to contain not less than 15 per cent tar acids. Each consignment
of crude carbolic acid received was assayed at the laboratory to
determine its specific gravity and percentage of tar acids, for it
is necessary to keep the product of a specific gravity approximately
that of water, so that it will diffuse rapidly and neither sink to
the bottom, nor remain at the surface.
In a hundred square miles of territory treated we used about two
hundred barrels of this mixture a month. The cost of manufacture was
about seventeen cents a gallon. In the early days we had used various
proprietary articles for this purpose, for which we generally had
to pay about fifty cents per gallon. Larvacide came in the course
of time to be used on the Isthmus for disinfectant purposes of many
kinds, and also for the prevention of fly-breeding. We found it most
excellent for all rough purposes of this kind, such as disinfecting
and deodorizing around privy vaults and similar places.
A sanitary inspector, when malaria is rife, has to be thoroughly
familiar with the life history of the mosquito, and particularly
with the life history of the anopheles. There are some six or seven
hundred species of mosquitoes, and many of these differ widely in
their habits of flight. The stegomyia mosquito is one of the feeblest
species in its ability for flight, and it is at once blown away and
destroyed when it gets into a breeze. It therefore seldom wanders
from the house in which it is bred. The culex solicitans is very
strong and bold in flight, and can fly twenty miles in one night
before a favoring breeze. This has been demonstrated by Dr. J. B.
Smith, of New Jersey. Dr. Smith was the entomologist of the state
of New Jersey, and one of the most faithful and successful mosquito
workers.
The culex solicitans is the common gray mosquito which breeds
so abundantly in the salt-water marshes of our Atlantic coast.
The different species of mosquitoes differ widely as to their
breeding-places, some species breeding in brackish water, some
only in fresh water. Other species breed freely in dirty and muddy
water, and still others can apparently live only in fresh, clean
water. The two species with which we are most concerned as being
disease-carrying mosquitoes are very particular as to their habits,
always seeking fresh, clean, clear water in which their larvæ can
develop.
The stegomyia likes clean rain water such as is found in cisterns
and water barrels. As these collections are found principally around
the dwellings of man in towns and cities, this mosquito is known as
a town mosquito. The larvæ of the anopheles, the malarial mosquito,
also likes clear, clean, fresh water, but it requires algæ and grass
for its protection. These conditions are best furnished by the
edges of ponds and running streams. This mosquito is, therefore,
essentially a country mosquito.
Generally, in any one locality, there are only three or four species
of mosquito occurring in any abundance, so that when the inspector
has learned to differentiate these, he is pretty well educated for
work in that particular locality. Each species usually has some
prominent trait; the anopheles, for instance, has the hind legs very
much longer than the fore legs, which gives her when at rest the
appearance of standing on her head. The stegomyia has prominent white
markings on its body and white bands around the joints of its legs,
and while these cannot readily be distinguished by the naked eye,
they give it a gray appearance which easily distinguishes it from
other species in such a locality as Panama.
The culex solicitans and stegomyia look very much alike to the
naked eye, so much so that one of our most experienced inspectors
at Panama, on returning from a vacation spent on Long Island, told
me that the stegomyia was the common mosquito on Long Island. As
a matter of fact, the stegomyia never appears farther north than
Norfolk, Virginia, unless as a matter of accidental introduction
during warm summer weather.
As the inspector deals with the mosquito in the larval stage
principally, he must be familiar with the habits of the larvæ, and
the habits of the different larvæ differ about as much as the habits
of the adult mosquitoes. They also differ much in size and shape;
for instance, the larvæ of the anopheles can readily be recognized
by the way it comes to the surface to breathe. During this process
it lies horizontal to and in contact with the surface of the water.
The culex larvæ, when breathing, lies with its tail up and head down.
The anopheles is a long, very slender larva; the culex, short and
chunky. The anopheles larva is most noticeable from its superior
intelligence. It will dive and seek shelter in the grass at any sound
or shadow thrown upon the water; the culex larva is sluggish and pays
little attention to such things.
[Illustration: Old French Engine Tender Used as Storage Tank for Oil]
[Illustration: Mule for Packing Oil to Oilers.]
The inspector must become very familiar with the half-dozen most
frequently occurring larvæ in his district; he must recognize them
easily when he sees them, and must know the kind of locality in
which to seek for them. He must learn the peculiarity of ditching as
applied to drainage intended to prevent mosquito breeding. This is
quite an art in itself. Take, for instance, an ordinary depression
between two small hills; if we want merely to get the water away
for ordinary drainage purposes, a ditch through the center will
accomplish this, but sometimes where the water is oozing through the
surface on the hillside, you still have soft moist places on each
side of your ditch which makes most excellent breeding-places for
mosquitoes.
Mr. Le Prince discovered that for mosquito work ditches would have to
be run along the hillside to cut off the water from this soft ground
and to catch it when it came to the surface. Where the ordinary
engineer does ditching, such a detail as this is overlooked by him.
Wherever possible, I insisted upon the sanitary inspector who was
instructed in these matters doing his own work, using men employed
directly by himself and under his orders and supervision. I think
it is of the utmost importance in mosquito work that the health
officer should have direct control of the men doing this work. The
ordinary engineer has no special knowledge of the life history of the
mosquito, and as the ditching and brush-cutting are done to prevent
mosquito-breeding, it is not surprising that it is not successfully
done by a man who has no knowledge of the mosquito.
All the work at Havana was done by men trained and instructed as to
the life habits of the mosquito, and the same was the case for the
first three years at Panama, when the effective mosquito work was
done. Whenever speaking or writing on this subject I have insisted
upon the necessity of having the execution of the work in the hands
of men who have been trained in anti-malarial procedure.
Another duty of the inspector was to see that the houses were
properly screened, and that the screens were kept in effective
condition. The Commission had several thousand buildings scattered in
thirty or more towns, and it endeavored to keep all these buildings
mosquito-proof with wire netting. Mr. Wright, the architect of the
Commission, developed several very useful types of houses, well
adapted to a tropical country and for the use of wire netting. The
general plan was not to attempt to screen the doors and windows; such
screening is more or less imperfect, and with several entrances to a
house, it is impossible with any ordinary care to prevent the doors
being left open. Mr. Wright therefore planned his houses so that they
were screened in, having only one door of entrance. A house screened
in this way is very thoroughly protected against the mosquito. The
housekeeper, with very little attention, can keep closed the one
screen door that gives entrance to the house.
Another great advantage of such screening is that there is very
little interference with the circulation of the air. We used a
wire netting of sixteen strands to the inch. In the case of a
window screened with such wire, a large part of the air that would
ordinarily enter is kept out, and the interior of the house is made
hot and uncomfortable in a warm climate. With the whole side of the
veranda screened the amount of air kept out is not appreciable, and
at Panama there was no complaint that the screening interfered with
the ventilation.
Another very great advantage of this style of building was that the
galleries could be used as living- and sleeping-rooms, and this at
Panama was very generally the case. It was found that the cost of
screening the gallery was very little more than that of screening the
doors and windows. While screening the whole gallery required much
more wire netting, the work itself was very simple. Making the window
and door frames brought up the cost of screening them to about the
cost of screening the galleries.
Care must be taken as to the quality of the wire netting. We were
put to a great deal of expense at Panama by sometimes getting wire
netting that would last only two or three months. We finally adopted
a specification requiring that our netting should be at least ninety
per cent copper, allowing not more than ten per cent of non-corrosive
metals. All netting was carefully tested to see that it came within
these specifications. It was the very general opinion on the Isthmus
that houses thus screened protected us much more thoroughly from
insect life than is the case in most parts of the United States
during the summer months. The dwellers in these houses habitually sat
on the galleries, with electric lights burning, and would read for a
whole evening without being disturbed by any kind of insect.
The inspector had a man constantly employed patching holes and
looking after the condition of this wire screening. In our barracks,
in which forty or fifty Jamaican negroes lived, it was much more
difficult to keep the wire netting in repair, and to keep the
screened door of entrance closed, and some mosquitoes would always
get in, if there were any mosquitoes around. In many of our stations
we succeeded in entirely eliminating the mosquito, as in the
district of Ancon. In such districts it made little difference as
to the condition of the wire netting; in other districts where the
anti-malarial work had been curtailed, mosquitoes were troublesome,
and every day some would get into such barracks as I have described.
For these cases Mr. Le Prince and his assistants developed a very
effective method. They took an ordinary test tube, put at the bottom
of it a few pieces of ordinary rubber, dropped on this rubber a few
drops of chloroform and placed a small layer of absorbent cotton over
it to keep it in place. When the mouth of this test tube is placed
over the mosquito, she in a few seconds becomes narcotized by the
chloroform and dies.
This method of killing infected mosquitoes was developed by Mr. Le
Prince and his sanitary inspectors into one of our most effective
anti-malarial measures. It can be used where none of the other
anti-malarial measures is possible.
For instance, at one time we had railroad construction going on
near Diablo Hill. This hill is surrounded by fresh-water swamps on
three sides. We put a force of several hundred men to work on this.
They were fairly comfortably housed in ordinary box cars, the doors
and windows of which had been carefully screened with wire netting.
These cars were located at the foot of Diablo Hill, on the edge of
the swamp. No anti-malarial work having been done here up to this
time, anopheles were very numerous. The swamp was so extensive that
efficient anti-malarial work was not considered then practicable.
Prophylactic quinin in five-grain doses was being taken by these
men, but we knew from a recent experience in this same locality that
infection was so severe that prophylactic quinin alone would not
protect our men. We knew, also, that a certain number of mosquitoes
would get by the screens every night. With a number of men living
in a car and using one door, we knew that on the average that door
would be open a large portion of the time. From inspections, we had
found that there were always a considerable number of mosquitoes in
the cars. Mr. Le Prince reasoned that while the mosquito-catcher
could not by any possibility catch all the mosquitoes in every
car every day, he would catch most of them. It was therefore
extremely improbable that any individual mosquito would escape the
mosquito-catcher for ten successive days. As it takes ten days from
the time at which the female anopheles mosquito bites the man sick
with malaria until she herself becomes able to transmit the disease,
no mosquito would live long enough under these conditions to become
disease-bearing. And in practice this proved to be the case. The
mosquito-catcher went through the cars every day and caught all the
mosquitoes he could find, and continued this day after day as long as
the cars remained in this swamp. The force was kept here for several
months without suffering appreciably from malaria.
This was the more impressive from the fact that just before we had
our negro employees in cars on the edge of the swamp, we had kept
a considerable force of marines for several weeks camped in tents
on top of Diablo Hill. These marines suffered very severely from
malarial fever, very few of them escaping. The tents not being
screened, we could not carry out the same method of catching infected
mosquitoes which was so successful in the case of our negro laborers,
a couple of hundred yards distant from this same camp. One of the
medical officers reported to me one day that, under a mosquito-bar
which he had kept over a sick man during the preceding night, he
caught in the morning quite a large number of anopheles—about fifty,
as I recall it. We used this method more and more during the later
years of our work on the Isthmus.
It is quite feasible everywhere, by proper drainage, to eliminate
entirely the anopheles mosquito, and in several of our towns
and villages we succeeded in doing this, and could have done it
everywhere if it had been thought desirable by the authorities to
apply the same methods, which had been successful at these places,
and previously at Havana.
At stations where mosquitoes were more or less troublesome, the
mosquito-catching method above described was very useful in the
barracks of the laborers. In a barrack building which quarters
forty or fifty men the best screening will not altogether keep
out mosquitoes, if there are many mosquitoes around. Holes will
continually be punched in the wire netting, but mosquitoes enter
principally through the constant opening of the door, and through the
door being carelessly left open. We found that at such stations we
could keep malaria down by catching malarial mosquitoes.
Occasionally, at a station where we had controlled mosquitoes for
several years, a great swarm would appear for reasons which we could
not explain. These swarms would not remain for a long time, and
usually they were not made up of anopheles. While they lasted, we
used the method of catching infected mosquitoes for the protection
of our force. On one occasion, however, we had a large flight of
anopheles. They swarmed everywhere about the station, and we could
not account for them, or discover where they came from. The sanitary
inspectors’ department devoted all its spare force to investigating
this point, and for a considerable period Mr. Le Prince devoted all
his time to the subject. He finally located the breeding area in a
small swamp about a mile from the town. This swamp had existed there
during the preceding years when Gatun had been comparatively free
from mosquitoes. At this particular time when the anopheles were so
troublesome, the engineers had begun to pump silt from the channel of
the Canal into this swamp. This silt was carried by salt water, which
made the water of the swamp brackish. This brackish water apparently
favored the development of the anopheles, and they were produced in
enormous numbers. The engineers were requested to pump sea water into
the swamp area for a few days. This soon made the water of the swamp
too salty for the breeding of the anopheles, and in a few days the
mosquitoes disappeared from the town.
It is remarkable that anopheles should have bred in this brackish
water, as it is a mosquito which generally seeks fresh water. It is
probable that the brackish water made some advantageous change in the
food supply of the larvæ, and that when the swamp was filled with
pure sea water, this food supply was stopped. This is the longest
flight of anopheles which we discovered on the Isthmus.
The method worked out by Mr. Le Prince and his assistants was
original with them. They would take a screened cage containing a
large number of anopheles mosquitoes, and spray them with a solution
of analine blue; take them down at night and release them at the
suspected spot. They would erect a tent at some convenient place in
the town to be examined, put a mosquito-bar in this tent with a man
under it as a bait for the lady anopheles, leave the bar open during
the night, closing it early in the morning before the anopheles
which had bitten during the night had an opportunity to escape. The
mosquitoes under the bar were caught and carefully examined. If any
blue-stained mosquitoes were found, it was proof that they had come
from the point at which the stained mosquitoes had been released the
evening before.
The job of acting as bait for the mosquitoes during these
investigations was a position much sought after by our negro
employees. They were paid by the hour the same wages that the
day-laborers received. To be paid full wages for sleeping in a
comfortable bed struck the Jamaican as being as near complete bliss
as was to be found in this world.
Mr. Le Prince did a great deal of work in experimenting upon
the flight of the anopheles at other stations, and during his
investigations came across many curious things as to the habits and
tastes of the anopheles. He found that the anopheles would show a
marked preference for a particular horse; though there might be
several other horses near and accessible, they would bite this one
horse almost exclusively, the taste of whose blood they seemed
to prefer. The same thing was true of men. We had one inspector
of whom the mosquitoes were excessively fond. When they were not
very numerous, they would scarcely trouble his companions at all,
devoting all their attention to him. This poor fellow died as a
result of this kind of work. He was Mr. Le Prince’s main dependence
for investigations of this kind. He did not suffer particularly
from malarial fever while on the Isthmus, but a short time after
his return to his northern home, he died of an attack of pernicious
malarial fever.
These various methods of combating malaria were very successful.
In some of the towns, as I have already said, they were just as
successful as they had been in the city of Havana, and I myself
have no doubt that, if we could have continued the methods which we
inaugurated on the Isthmus, we should have been just as successful
with malaria at Panama as we had previously been with the disease
at Havana, and at no greater cost. As it was, we succeeded in so
protecting the force against malaria that it did not interfere to any
appreciable degree with its working capacity.