I have wished for a few things in my life, none of them capable of
interfering with the common weal. I have longed to possess a pond,
screened from the indiscretion of the passers by, close to my house,
with clumps of rushes and patches of duckweed. Here, in my leisure
hours, in the shade of a willow, I should have meditated upon aquatic
life, a primitive life, easier than our own, simpler in its affections
and its brutalities. I should have watched the unalloyed happiness of
the mollusk, the frolics of the Whirligig, the figure-skating of the
Hydrometra [a water bug known as the Pond skater], the dives of the
Dytiscus beetle, the veering and tacking of the Notonecta [the water
boatman], who, lying on her back, rows with two long oars, while her
short forelegs, folded against her chest, wait to grab the coming prey.
I should have studied the eggs of the Planorbis, a glairy nebula wherein
focuses of life are condensed even as suns are condensed in the nebulae
of the heavens. I should have admired the nascent creature that turns,
slowly turns in the orb of its egg and describes a volute, the draft,
perhaps, of the future shell. No planet circles round its center of
attraction with greater geometrical accuracy.
I should have brought back a few ideas from my frequent visits to the
pond. Fate decided otherwise: I was not to have my sheet of water. I
have tried the artificial pond, between four panes of glass. A poor
shift! Our laboratory aquariums are not even equal to the print left in
the mud by a mule's hoof, when once a shower has filled the humble basin
and life has stocked it with its marvels.
In spring, with the hawthorn in flower and the crickets at their
concerts, a second wish often came to me. Along the road, I light upon a
dead mole, a snake killed with a stone, victims both of human folly.
The mole was draining the soil and purging it of its vermin. Finding him
under his spade, the laborer broke his back for him and flung him over
the hedge. The snake, roused from her slumber by the soft warmth of
April, was coming into the sun to shed her skin and take on a new one.
Man catches sight of her: 'Ah, would you?' says he. 'See me do something
for which the world will thank me!'
And the harmless beast, our auxiliary in the terrible battle which
husbandry wages against the insect, has its head smashed in and dies.
The two corpses, already decomposing, have begun to smell. Whoever
approaches with eyes that do not see turns away his head and passes
on. The observer stops and lifts the remains with his foot; he looks. A
world is swarming underneath; life is eagerly consuming the dead. Let us
replace matters as they were and leave death's artisans to their task.
They are engaged in a most deserving work.
To know the habits of those creatures charged with the disappearance of
corpses, to see them busy at their work of disintegration, to follow
in detail the process of transmutation that makes the ruins of what has
lived return apace into life's treasure house: these are things that
long haunted my mind. I regretfully left the mole lying in the dust of
the road. I had to go, after a glance at the corpse and its harvesters.
It was not the place for philosophizing over a stench. What would people
say who passed and saw me!
And what will the reader himself say, if I invite him to that sight?
Surely, to busy one's self with those squalid sextons means soiling
one's eyes and mind? Not so, if you please! Within the domain of our
restless curiosity, two questions stand out above all others: the
question of the beginning and the question of the end. How does matter
unite in order to assume life? How does it separate when returning to
inertia? The pond, with its Planorbis eggs turning round and round,
would have given us a few data for the first problem; the Mole, going
bad under conditions not too repulsive, will tell us something about the
second: he will show us the working of the crucible wherein all things
are melted to begin anew. A truce to nice delicacy! Odi profanum vulgus
et arceo; hence, ye profane: you would not understand the mighty lesson
of the rag tank.
I am now in a position to realize my second wish. I have space, air and
quiet in the solitude of the harmas. None will come here to trouble me,
to smile or to be shocked at my investigations. So far, so good; but
observe the irony of things: now that I am rid of passers by, I have to
fear my cats, those assiduous prowlers, who, finding my preparations,
will not fail to spoil and scatter them. In anticipation of their
misdeeds, I establish workshops in midair, whither none but genuine
corruption agents can come, flying on their wings. At different points
in the enclosure, I plant reeds, three by three, which, tied at their
free ends, form a stable tripod. From each of these supports, I hang, at
a man's height, an earthenware pan filled with fine sand and pierced at
the bottom with a hole to allow the water to escape, if it should rain.
I garnish my apparatus with dead bodies. The snake, the lizard, the toad
receive the preference, because of their bare skins, which enable me
better to follow the first attack and the work of the invaders. I ring
the changes with furred and feathered beasts. A few children of the
neighborhood, allured by pennies, are my regular purveyors. Throughout
the good season, they come running triumphantly to my door, with a snake
at the end of a stick, or a lizard in a cabbage leaf. They bring me the
rat caught in a trap, the chicken dead of the pip, the mole slain by
the gardener, the kitten killed by accident, the rabbit poisoned by some
weed. The business proceeds to the mutual satisfaction of sellers and
buyer. No such trade had ever been known before in the village nor ever
will be again.
April ends; and the pans rapidly fill. An ant, ever so small, is the
first arrival. I thought I should keep this intruder off by hanging my
apparatus high above the ground: she laughs at my precautions. A few
hours after the deposit of the morsel, fresh still and possessing no
appreciable smell, up comes the eager picker-up of trifles, scales the
stems of the tripod in processions and starts the work of dissection.
If the joint suits her, she even goes to live in the sand of the pan and
digs herself temporary platforms in order to work the rich find more at
her ease.
All through the season, from start to finish, she will always be the
promptest, always the first to discover the dead animal, always the last
to beat a retreat when nothing more remains than a heap of little bones
bleached by the sun. How does the vagabond, passing at a distance, know
that, up there, invisible, high on the gibbet, there is something worth
going for? The others, the real knackers, wait for the meat to go bad;
they are informed by the strength of the effluvia. The ant, gifted with
greater powers of scent, hurries up before there is any stench at all.
But, when the meat, now two days old and ripened by the sun, exhales its
flavor, soon the master ghouls appear upon the scene: Dermestes [bacon
beetles, small flesh-eating beetles] and Saprini [exceedingly small
flesh-eating beetles], Silphae [carrion beetles] and Necrophori [burying
beetles], flies and Staphylini [rove beetles], who attack the corpse,
consume it and reduce it almost to nothing. With the ant alone, who
each time carries off a mere atom, the sanitary operation would take too
long; with them, it is a quick business, especially as certain of them
understand the process of chemical solvents.
These last, who are high class scavengers, are entitled to first
mention. They are flies, of many various species. If time permitted,
each of those strenuous ones would deserve a special examination; but
that would weary the patience of both the reader and the observer. The
habits of one will give us a summary notion of the habits of the rest.
We will therefore confine ourselves to the two principal subjects,
namely, the Luciliae, or greenbottles, and the Sarcophagae, or grey
flesh flies.
The Luciliae--flies that glitter--are magnificent flies known to all of
us. Their metallic luster, generally a golden green, rivals that of our
finest beetles, the Rosechafers, Buprestes and leaf beetles. It gives
one a shock of surprise to see so rich a garb adorn those workers in
putrefaction. Three species frequent my pans: Lucilia Caesar, LIN., L.
cadaverina, LIN., and L. cuprea, ROB. The first two, both of whom are
gold-green, are plentiful; the third, who sports a coppery luster, is
rare. All three have red eyes, set in a silver border.
Lucilia Caesar is larger than L. cadaverina and also more forward in her
business. I catch her in labor on the 23rd of April. She has settled
in the spinal canal of a neck of mutton and is laying her eggs on the
marrow. For more than an hour, motionless in the gloomy cavity, she goes
on packing her eggs. I can just see her red eyes and her silvery face.
At last, she comes out. I gather the fruit of her labor, an easy matter,
for it all lies on the marrow, which I extract without touching the
eggs.
A census would seem important. To take it at once is impracticable: the
germs form a compact mass, which would be difficult to count. The best
thing is to rear the family in a jar and to reckon by the pupae buried
in the sand. I find a hundred and fifty-seven. This is evidently but
a minimum; for Lucilia Caesar and the others, as the observations that
follow will tell me, lay in packets at repeated intervals. It is a
magnificent family, promising a fabulous legion to come.
The greenbottles, I was saying, break up their laying into sections. The
following scene affords a proof of this. A Mole, shrunk by a few days'
evaporation, lies spread upon the sand of the pan. At one point, the
edge of the belly is raised and forms a deep arch. Remark that the
Greenbottles, like the rest of the flesh eating flies, do not trust
their eggs to uncovered surfaces, where the heat of the sun's rays might
endanger the existence of the delicate germs. They want dark hiding
places. The favorite spot is the lower side of the dead animal, when
this is accessible.
In the present case, the only place of access is the fold formed by the
edge of the belly. It is here and here alone that this day's mothers
are laying. There are eight of them. After exploring the piece and
recognizing its good quality, they disappear under the arch, first this
one, then that, or else several at a time. They remain under the Mole
for a considerable while. Those outside wait, but go repeatedly to the
threshold of the cavern to take a look at what is happening within and
see whether the earlier ones have finished. These come out at last,
perch on the animal and wait in their turn. Others at once take their
place in the recesses of the cave. They remain there for some time and
then, having done their business, make room for more mothers and come
forth into the sunlight. This going in and out continues throughout the
morning.
We thus learn that the laying is effected by periodical emissions,
broken with intervals of rest. As long as she does not feel ripe eggs
coming to her oviduct, the greenbottle remains in the sun, hovering to
and fro and sipping modest mouthfuls from the carcass. But, as soon as a
fresh stream descends from her ovaries, quick as lightning she makes for
a propitious site whereon to deposit her burden. It appears to be the
work of several days thus to divide the total laying and to distribute
it at different points.
I carefully raise the animal under which these things are happening.
The egg laying mothers do not disturb themselves; they are far too busy.
Their ovipositor extended telescope fashion, they heap egg upon egg.
With the point of their hesitating, groping instrument, they try to
lodge each germ, as it comes, farther into the mass. Around the serious,
red-eyed matrons, the Ants circle, intent on pillage. Many of them make
off with a greenbottle egg between their teeth. I see some who, greatly
daring, effect their theft under the ovipositor itself. The layers do
not put themselves out, let the ants have their way, remain impassive.
They know their womb to be rich enough to make good any such larceny.
Indeed, what escapes the depredations of the ants promises a plenteous
brood. Let us come back a few days later and lift the mole again.
Underneath, in a pool of sanies, is a surging mass of swarming sterns
and pointed heads, which emerge, wriggle and dive in again. It suggests
a seething billow. It turns one's stomach. It is horrible, most
horrible. Let us steel ourselves against the sight: it will be worse
elsewhere.
Here is a fat snake. Rolled into a compact whorl, she fills the whole
pan. The greenbottles are plentiful. New ones arrive at every moment
and, without quarrel or strife, take their place among the others,
busily laying. The spiral furrow left by the reptile's curves is the
favorite spot. Here alone, in the narrow space between the folds, are
shelters against the heat of the sun. The glistening Flies take their
places, side by side, in rows; they strive to push their abdomen and
their ovipositor as far forward as possible, at the risk of rumpling
their wings and cocking them towards their heads. The care of the person
is neglected amid this serious business. Placidly, with their red eyes
turned outwards, they form a continuous cordon. Here and there, at
intervals, the rank is broken; layers leave their posts, come and
walk about upon the snake, what time their ovaries ripen for another
emission, and then hurry back, slip into the rank and resume the flow of
germs. Despite these interruptions, the work of breeding goes fast. In
the course of one morning, the depths of the spiral furrow are hung
with a continuous white bark, the heaped up eggs. They come off in great
slabs, free of any stain; they can be shoveled up, as it were, with
a paper scoop. It is a propitious moment if we wish to follow the
evolution at close quarters. I therefore gather a profusion of this
white manna and lodge it in glass tubes, test tubes and jars, with the
necessary provisions.
The eggs, about a millimeter long, are smooth cylinders, rounded at
both ends. They hatch within twenty-four hours. The first question that
presents itself is this: how do the greenbottle grubs feed? I know quite
well what to give them, but I do not in the least see how they manage to
consume it. Do they eat, in the strict sense of the word? I have reasons
to doubt it.
Let us consider the grub grown to a sufficient size. It is the usual
fly larva, the common maggot, shaped like an elongated cone, pointed in
front, truncated behind, where two little red spots show, level with the
skin: these are the breathing holes. The front, which is called the
head by stretching a word--for it is little more than the entrance to an
intestine--the front is armed with two little black hooks, which slide
in a translucent sheath, project a little way outside and go in turn by
turn. Are we to look upon these as mandibles? Not at all, for, instead
of having their points facing each other, as would be required in a
real mandibular apparatus, the two hooks work in parallel directions
and never meet. What they are is ambulatory organs, grapnels assisting
locomotion, which give a purchase on the plane and enable the animal to
advance by means of repeated contractions. The maggot walks with the aid
of what a superficial examination would pronounce to be a machine
for eating. It carries in its gullet the equivalent of the climber's
alpenstock.
Let us hold it, on a piece of flesh, under the lens. We shall see it
walking about, raising and lowering its head and, each time, stabbing
the meat with its pair of hooks. When stationary, with its crupper at
rest, it explores space with a continual bending of its fore part; its
pointed head pokes about, jabs forward, goes back again, producing and
withdrawing its black mechanism. There is a perpetual piston play. Well,
look as carefully and conscientiously as I please, I do not once see the
weapons of the mouth tackle a particle of flesh that is torn away and
swallowed. The hooks come down upon the meat at every moment, but never
take a visible mouthful from it. Nevertheless, the grub waxes big and
fat. How does this singular consumer, who feeds without eating, set
about it? If he does not eat, he must drink; his diet is soup. As meat
is a compact substance, which does not liquefy of its own accord, there
must, in that case, be a certain recipe to dissolve it into a fluid
broth. Let us try to surprise the maggot's secret.
In a glass tube, sealed at one end, I insert a piece of lean flesh, the
size of a walnut, which I have drained of its juices by squeezing it in
blotting paper. On the top of this, I place a few slabs of greenbottle
eggs collected a moment ago from the snake in my earthen pan. The number
of germs is, roughly, two hundred. I close the tube with a cotton plug,
stand it upright, in a shady corner of my study, and leave things to
take their course. A control tube, prepared like the first, but not
stocked with maggots, is placed beside it.
As early as two or three days after the hatching, I obtain a striking
result. The meat, which was thoroughly drained by the blotting paper,
has become so moist that the young vermin leave a wet mark behind them
as they crawl over the glass. The swarming brood creates a sort of mist
with the crossing and criss-crossing of its trails. The control tube,
on the contrary, keeps dry, proving that the moisture in which the worms
move is not due to a mere exudation from the meat.
Besides, the work of the maggot becomes more and more evident.
Gradually, the flesh flows in every direction like an icicle placed
before the fire. Soon, the liquefaction is complete. What we see is no
longer meat, but fluid Liebig's extract. If I overturned the tube, not a
drop of it would remain.
Let us clear our minds of any idea of solution by putrefaction, for in
the second tube a piece of meat of the same kind and size has remained,
save for color and smell, what it was at the start. It was a lump and
it is a lump, whereas the piece treated by the worms runs like melted
butter. Here we have maggot chemistry able to rouse the envy of
physiologists when studying the action of the gastric juice.
I obtain better results still with hard-boiled white of egg. When cut
into pieces the size of a hazel nut and handed over to the greenbottle's
grubs, the coagulated albumen dissolves into a colorless liquid which
the eye might mistake for water. The fluidity becomes so great that, for
lack of a support, the worms perish by drowning in the broth; they are
suffocated by the immersion of their hind part, with its open breathing
holes. On a denser liquid, they would have kept at the surface; on this,
they cannot.
A control tube, filled in the same way, but not colonized, stands beside
that in which the strange liquefaction takes place. The hardboiled white
of egg retains its original appearance and consistency. In course of
time, it dries up, if it does not turn moldy; and that is all.
The other quaternary compounds performing the same functions as
albumen--the gluten of cereals, the fibrin of blood, the casein of
cheese and the legumin of chickpeas--undergo a similar modification, in
varying degrees. Fed, from the moment of leaving the egg, on any one of
these substances, the worms thrive very well, provided that they escape
drowning when the gruel becomes too clear; they would not fare better
on a corpse. And, as a general rule, there is not much danger of going
under: the matter only half liquefies; it becomes a running pea soup,
rather than an actual fluid.
Even in this imperfect case, it is obvious that the greenbottle grubs
begin by liquefying their food. Incapable of taking solid nourishment,
they first transform the spoil into running matter; then, dipping their
heads into the product, they drink, they slake their thirst, with long
sups. Their dissolvent, comparable in its effects with the gastric juice
of the higher animals, is, beyond a doubt, emitted through the mouth.
The piston of the hooks, continually in movement, never ceases spitting
it out in infinitesimal doses. Each spot touched receives a grain of
some subtle pepsin, which soon suffices to make that spot run in every
direction. As digesting, when all is said, merely means liquefying,
it is no paradox to assert that the maggot digests its food before
swallowing it.
These experiments with my filthy, evil smelling tubes have given me some
delightful moments. The worthy Abbe Spallanzani must have known some
such when he saw pieces of raw meat begin to run under the action of the
gastric juice which he took, with pellets of sponge, from the stomachs
of crows. He discovered the secrets of digestion; he realized in a glass
tube the hitherto unknown labors of gastric chemistry. I, his distant
disciple, behold once more, under a most unexpected aspect, what struck
the Italian scientist so forcibly. Worms take the place of the crows.
They slaver upon meat, gluten, albumen; and those substances turn to
fluid. What our stomach does within its mysterious recesses the maggot
achieves outside, in the open air. It first digests and then imbibes.
When we see it plunging into the carrion broth, we even wonder if it
cannot feed itself, at least to some extent, in a more direct fashion.
Why should not its skin, which is one of the most delicate, be capable
of absorbing? I have seen the egg of the sacred beetle and other dung
beetles growing considerably larger--I should like to say, feeding--in
the thick atmosphere of the hatching chamber. Nothing tells us that the
grub of the greenbottle does not adopt this method of growing. I picture
it capable of feeding all over the surface of its body. To the gruel
absorbed by the mouth it adds the balance of what is gathered and
strained through the skin. This would explain the need for provisions
liquefied beforehand.
Let us give one last proof of this preliminary liquefaction. If the
carcass--mole, snake or another--left in the open air have a wire gauze
cover placed over it, to keep out the flies, the game dries under a hot
sun and shrivels up without appreciably wetting the sand on which it
lies. Fluids come from it, certainly, for every organized body is a
sponge swollen with water; but the liquid discharge is so slow and
restricted in quantity that the heat and the dryness of the air disperse
it as it appears, while the underlying sand remains dry, or very nearly
so. The carcass becomes a sapless mummy, a mere bit of leather. On the
other hand, do not use the wire gauze cover, let the flies do their work
unimpeded; and things forthwith assume another aspect. In three or four
days, an oozing sanies appears under the animal and soaks the sand to
some distance.
I shall never forget the striking spectacle with which I conclude this
chapter. This time, the dish is a magnificent Aesculapius' snake, a yard
and a half long and as thick as a wide bottleneck. Because of its size,
which exceeds the dimensions of my pan, I roll the reptile in a double
spiral, or in two storeys. When the copious joint is in full process
of dissolution, the pan becomes a puddle wherein wallow, in countless
numbers, the grubs of the greenbottle and those of Sarcophaga carnaria,
the Grey or checkered flesh fly, which are even mightier liquefiers. All
the sand in the apparatus is saturated, has turned into mud, as though
there had been a shower of rain. Through the hole at the bottom, which
is protected by a flat pebble, the gruel trickles drop by drop. It is a
still at work, a mortuary still, in which the Snake is being drawn off.
Wait a week or two; and the whole will have disappeared, drunk up by the
sun: naught but the scales and bones will remain on a sheet of mud.
To conclude: the maggot is a power in this world. To give back to life,
with all speed, the remains of that which has lived, it macerates and
condenses corpses, distilling them into an essence wherewith the earth,
the plant's foster mother, may be nourished and enriched.