SERVICES RENDERED TO SCIENCE AND HUMANITY BY EXPERIMENTAL PHYSIOLOGY
I now come to a favourite theme of anti-vivisectionists, viz., that
experimental physiology has produced nothing, and that the differences of
opinion among _savants_ are so considerable that this alone proves the
impossibility of vivisection ever establishing anything permanent.
Here again it is difficult to reply because of the very ignorance of the
honourable gentlemen who criticise us. Most certainly there still remain
many disputed and disputable points in physiology, and nothing is easier
than to find therein striking and abundant contradictions. If we wished to
amuse ourselves, we might write five or six big volumes on the subject; but
let us leave this tedious and useless labour to the anti-vivisectionists to
accomplish to their hearts' content. I prefer to tell them, what they do
not wish to know perhaps, that contradiction is the very essence of
science. As our demonstrations appeal not to faith but to reason; as we
admit free discussion, free investigation from every side; any proposition
must have multitudinous and positive proofs in its favour before it can be
adopted without hesitation. Even our opinions were never prescribed by
faith or violence; we take pleasure in provoking discussion and
contradiction. With our adversaries' leave be it said that a dogmatic,
irreproachable book, where there was no place for hesitation or doubt,
would be the very negation of science. Even the treatises of geometry and
mechanics, although non-experimental, rational sciences, sometimes
contradict themselves. It has been rightly said that the history of science
is the history of human errors--errors which, little by little, draw nearer
and nearer to supreme truth without ever attaining it. We must understand
this, or we shall be rebelling against the conception of scientific truth.
Now, in treatises on physiology, we find a number of well-demonstrated
truths, and a still larger number of truths only half demonstrated, and,
consequently, contested. Our successors will also certainly find in our
books of to-day an enormous number of errors.
What conclusion is to be drawn from this fact? Have those who reproach the
science of physiology with being only a tissue of contradictions and errors
ever opened a book on physiology (for example, the text-book of Schaefer,
in two large, compact, closely written volumes of 1000 pages each)? They
would there find thousands of positive, incontestable facts on all the
questions which concern physiology.
Let us take, each in its turn, the great functions of life, and we shall
see that they have become known only by experimentation.
1. _The Circulation of the Blood_, suspected by Michel Servet, Realdo
Colombo, and Andreas Cesalpin, was really established by Harvey in 1628.
Yet Harvey was only able to demonstrate it by experiments performed on the
living bodies of frogs and deer. Since Harvey's time, the laws of the
circulation have been established with admirable precision. Hales
demonstrated the pressure of blood in the vessels. Chauveau and Marey
introduced into the heart of a horse an apparatus which enabled the
pressure of the blood in the heart, in the arteries, and in the veins, to
be measured. Weber found that the pneumogastric nerve stopped the heart's
action. Ludwig applied the graphic method to the circulation. Delicate
instruments have been constructed which give diagrams of the pulsations and
measure the pressure of the blood in the arteries and in the heart of man.
Claude Bernard discovered the nerves which regulate the movements of the
vessel walls. In short, the whole history of the circulation is due solely
to vivisections, and it would be ridiculous to speak of our uncertainties
in this respect; for the essential mechanical or nervous laws of the
circulation are as well known now as those of the combinations of nitrogen
with oxygen.
2. _The Respiration_ remained profoundly unknown, as to its inmost nature,
right up to Lavoisier's time. Lavoisier placed some guinea-pigs in a box
filled with ice, measured the quantity of heat thrown off, the quantity of
oxygen consumed, the quantity of carbonic acid produced; and he was thus
able to deduce a fundamental law of life, viz., that life is essentially
combustion. He made experiments on himself also; but however great one's
respect for the life of a guinea-pig may be, must it be considered wrong
that Lavoisier should have experimented on the guinea-pig before
experimenting on himself?
As for the laws which regulate this consumption of oxygen and this
production of carbonic acid, to discover these it was necessary to put into
cages animals of every species and of every size. And there is, perhaps,
not a single physiologist who has not made this experiment, at the risk of
annoying the cats and dogs thus exposed--without, as far as that goes,
doing them any harm--to varied temperatures or to different diets.
Moreover, in order to study the respiratory exchanges, physiologists
experiment on man as well; is, therefore, the extraordinary scruple against
experimenting on animals to be imposed upon them also?
To take an excellent example of the services which experimental physiology
can render not to science only--which would, indeed, be quite sufficient
to justify them--but to humanity, I will cite the experiments of Paul Bert
with relation to elevated atmospheric pressures. There are certain workmen
who are obliged to work under water, at a depth of 20 to 30 yards, for the
construction of piers and bridges, or the exploration of sunken vessels.
Now, it had long been observed that some of these men died suddenly on
returning to the surface. Experimental physiology was able to discover the
cause of that sudden death. When a man (or an animal), after having been
subjected to several times the normal atmospheric pressure, is suddenly
released from this pressure, the nitrogen dissolved in the blood is
disengaged suddenly: this produces gaseous embolism, that is to say,
bubbles of gas are formed, which block the blood-vessels and prevent the
blood circulating in the capillaries. Knowing this, the death of men
working at a pressure of four atmospheres could then be avoided by
releasing them slowly, that is by bringing them slowly back to the normal
atmospheric pressure. Is it barbarous to attach more importance to the
death of these men than to the death of the few dogs and mice that served
to establish this law?
I was able to demonstrate that, if the temperature of the air is very high,
as in the hottest days of summer, dogs that are muzzled die rapidly of
hyperpyrexia (_i.e._ high fever), for they are no longer able to cool
themselves by panting. It is true that this experiment cost the lives of a
few dogs, but has it not saved many others by pointing out that dogs should
not be muzzled under certain conditions? It goes without saying I am not
speaking of the theoretical consequences of this experiment.
Artificial respiration, which can restore to life the apparently drowned,
is one, of the conquests of experimental physiology; for we have been able
to determine the best method and the essential conditions (for artificial
breathing) by experiments of a very precise nature. Is it nothing to know
how to restore to life the apparently drowned?
3. _The Process of Digestion_ has also been learned solely by experiment.
In the history of science there are two or three cases of individuals in
whom a wound or an operation has produced a gastric fistula, that is to say
an abdominal opening through which the stomach can be reached and food
introduced. Had we remained satisfied with these accidental observations,
we should have obtained but mediocre results. Physiologists therefore have
made experimental gastric fistulae. Dogs thus operated on, after an illness
of a few days, recover thoroughly. Some physiologists have kept dogs for
several years in this condition: gay, caressing, docile, they did not
appear to complain of their lot. They were better nourished, more petted
and loved than the many starving dogs which roam about the country. They
were not a whit more unhappy than was Alexis St Martin (observed in 1831 by
Dr Beaumont) and Marcellin (whom I observed in 1878, at the beginning of my
career). Quite recently an eminent Russian physiologist, Pawloff, has, by
making gastric fistulae in animals, been able to discover a number of
important facts, absolutely necessary to be known for the treatment of
diseases of the stomach, and even for the establishment of a normal
alimentation.
The problem of alimentation is, indeed, one of the most essential, perhaps
the most essential, in the history of humanity. I suppose that
anti-vivisectionists are aware of the fact that, even in Europe, large
populations exist who are insufficiently nourished. Under these conditions,
is it not desirable to know exactly the quantities of carbon, nitrogen,
salt, lime, and phosphorus which are necessary for animals, and
consequently for man? Should not anti-vivisectionists, interested in
vegetarianism, before venturing to institute a vegetable diet for man, try
it first of all upon carnivorous animals, so as to know how a mixed
alimentation can be modified by a vegetable alimentation, and to what
extent those modifications are compatible with health?
4. _The Nervous System_ is not so well known, so far as its functions are
concerned, as the circulatory system or the digestive system. Nevertheless,
positive discoveries are extremely numerous: the action of the nerves on
the glands and on the muscles; the part played by the different portions
of the brain; nervous degenerations; the laws governing reflex actions--all
this constitutes a formidable body of well-established facts. I do not
pretend that everything is known. Alas! No! There are still innumerable
truths to be discovered, and serious errors are doubtless most learnedly
taught, with many contradictions, much uncertainty, much confusion--all of
which simply proves that physiology is not a science whose last chapter has
yet been written, that the last word of this science has not yet been
pronounced. Nevertheless, blind indeed would the man be who would venture
to conclude that physiology was not a science; or to assert that physiology
is a science of little importance; that the role of the physiologist, from
the point of view of the alleviation of human miseries, is null; and that
knowledge of physiological facts is useless. Will it be claimed that the
doctor has no need of a knowledge of physiology? I will reply by a
comparison I am accustomed to make before my medical students when I wish
to make them understand the necessity of a sound physiological education.
Let us suppose that a watchmaker claimed to be able to cure disordered
watches, but at the same time declared himself unable to tell by what
springs and by what mysterious mechanism a healthy watch should mark the
hour; that watchmaker would inspire me with a very small amount of
confidence, and I would not go to him; for, until the contrary is proved to
me, I believe that an indispensable condition for repairing a watch when
out of order is to know how a watch should work when in good repair.
Physiology exists only because there have been physiologists. By that I do
not mean to say that all the truths of physiology are due exclusively to
vivisection. I only claim that physiology without vivisection would be
strangely clumsy, limited to a few empirical facts, and that, if
vivisection be proscribed, we must resolutely give up classing physiology
among the sciences. We may study the stars and the earth, electricity and
heat, geography and history, and are we to be forbidden to study the
functions of living matter? Such a proposal is obviously absurd, for of all
the sciences accessible to man, physiology is that which is nearest to
him.
It is only the ignorant who dare assert that experimentation on animals
cannot be applied to man. There are of course differences which
physiologists train themselves to perceive; for example, certain poisons
are almost innocuous to some animals, and are very fatal to man. The
alkaloid of belladonna, atropine, is a thousand times more toxic for a man
than for a goat. It is difficult to kill a goat with morphia, whilst a drop
of laudanum kills a new-born babe. Carbonic oxide is absolutely harmless
for the invertebrata which have no blood. Crayfish and snails live with
impunity in pure oxide of carbon. And I could cite a number of other facts
which are described in detail in every treatise of physiology or
pharmacology.
But what does it matter to us if we know it?--and we can nearly always know
it. There are functional differences between men and animals; and
physiologists know these perfectly well by their training; but there are,
above all things, much more striking resemblances. It would be, for
instance, ridiculous to suppose that oxygen did not dissolve in our blood
in about the same way in which it dissolves in the blood of a cat or a
rabbit; that the pneumogastric nerve, which stops the heart of the cat and
the rabbit, will not stop the heart of man; that the arterial pressure,
which is 16 c.m. of mercury in the horse, the dog, and the cat, is 1 c.m.
or 1.60 c.m. in man; that the transformation of albuminous matters into
urea takes place differently in the dog and in man. On the contrary,
everything goes to prove the general laws are the same, and that the
physiology of man, whilst not rigorously identical in every respect with
the physiology of the animal, is nevertheless sufficiently analogous to
enable a _general physiology_ to comprise in its vast laws the functions of
every living being, man, mammal, vertebrata, invertebrata, and even every
living cell.