A Letter from Mr.

Von Humboldt to M. H. Van Mons on the Chemical Process of Vitality; together with the Extract of a Letter from Citizen Fourcroy to Citizen Van Mons on the same Subject .

Annales de Chimie, XXII. 64.

I HAVE lately addressed several letters to Messrs. Dolomieu and Fourcroy at Paris, and perceive by those I have received from the former that mine have miscarried.

Permit me, Sir, to address myself to you.

By your means I may perhaps succeed in forwarding to Paris some explanations respecting facts which, as I understand, employ part of the time of the National Institute.

Be pleased to accept my assurances of the great respect which your zeal and your chemical discoveries have inspired me with.

The natural philosophers of Europe ought to form a single family.

They are in pursuit of the same interesting objects; and this is a sufficient motive to produce that useful degree of intimacy which is calculated to promote their researches.

You are probably acquainted with my Essays on the Vegetable Philosophy, such as my Aphorismi ex doctrina physiologiae chimicae plantarum, annexed to my Flora subterranea Fribergensis, and several memoirs which I have presented to the National Institute.The memoir on the action of oxygenated muriatic acid upon the vegetable and animal fibre, which is printed in the Magazin Encyclopedique of Millin, Noel, and Warens, seems to have had more success. I am happy to hear that Messrs. Vauquelin and my friend Dolomieu have begun to repeat my experiments.

As the memoir which was read to the National Institute related principally to the germination of vegetables, I have thought it my duty to announce to you certain facts more striking respecting the animal fibre.

The strongest stimulus of the nervous fibre is that of the alkalis.

It appears that these salts affect the irritable and sensible system by means of their azote.

Let the thigh of a frog be thrown into the oxygenated muriatic acid, or the nitric acid, and it will remain motionless. Let it be put into a solution of pot-ash, or of soda, and it will undergo contractions no less strong than when irritated by the metals.

These motions always commence at the lower extremities.

The toes move first, afterwards the musculus gastrocnemius, and then the thigh.

If the nerve be very sensible (for nothing more is required than simply to immerse the extremity of the crural nerve in the oleum tartari per deliquium), the contractions will end in an universal tension or rigidity.

The leg rises up perpendicularly, the membrane of the feet extends itself, and the tetanus appears.

In this situation all the irritability of the fibre appears to be extinguished; and if an electric stroke be passed through the limb, the exhaustion becomes real.

It is a striking phenomenon to see the last remaining signs of tetanus disappear in an instant.

But there is another method by which the tension disappears, and by which I am able to restore the irritability to the organs.

It seems that the acidifiable bases of the alkali, principally the azote, have consumed all the oxygene contained in the fibre.

The chemical process of vitality ceases.

If I pour an acid, for example the nitric acid, upon the nerve, an effervescence will take place; part of the alkali becomes latent, and the rest will have a proper proportion with respect to its oxygene.

From this moment the contraction with zinc and silver is again produced.

Increase the quantity of acid, and the movements are again weakened.

In this manner it is, that by forming an equilibrium between the azote of the alkali and the oxygene of the acid applied to the animal fibre, the irritability of the organs may be taken away or restored three or four times in succession.

You may easily perceive, Sir, that these experiments require steady attention.

The degree of insensibility to which the nerve is reduced by repeating them may be very different.

It is possible to determine exactly the quality of the chemical agents, their weight and temperature; notwithstanding which, many experiments do not succeed.

The reason is, that there are conditions which depend on the individuality of the organization, and concerning which we must still confess our total ignorance.

The influences of the oxygenated muriatic acid upon the animal fibre are less marked than those of the alkalis; but they are nevertheless of much importance.

I steeped the feet of a frog (I mention this animal by preference, though I have made the same experiments on other species) in a solution of opium in alcohol.

The metals, or galvanism, excited no motion.

I threw one leg into pure water, and the other into the oxygenated muriatic acid; the first remained motionless, the second gave very strong contractions, and shewed that its irritability was restored.

The common acids depress the irritability of the nervous fibre.

A crural nerve, rendered insensible by the ordinary muriatic acid, remains so though it has been steeped in the solution of pot-ash: but the mineral acids exhaust the forces of the muscles, by condensing the elements of the muscular fibre.

These acids act in the same manner as cold, which depresses the nerves, and is beneficial to the muscles.

The muscles and the nerves have specific stimuli, agreeable to the diversity of the elements.

The terrible action which the alkalis exercise on the nerves appears to explain the effect of the secretion of the seminal liquor on the blood.

It is this alkali which, distributed throughout the system, answers the purpose of a stimulus beneficial to the animal fibre.

By this action I account for the ferocity of the ichthyophagi.

My eldest brother, who is very skilful in the study of anatomy, applied zinc and silver to the mouth and the brain of a dead fish; it afforded no motion.

I poured oxygenated muriatic acid on the nerves, and at that instant the contractions became very strong.

Mr. Herz and several learned men of Berlin were present at these and many other experiments.

The heart of the same fish, which had entirely ceased to palpitate, began to perform this movement with regularity when I threw it into the oxygenated muriatic acid.

The same experiment succeeded very often with the hearts of frogs: when a heart is immersed in a solution of pot-ash, it loses its irritability for ever; so that azote is not the specific stimulus of the heart.

Mr. Pfaff, while employed in my experiments respecting germination in the oxygenated muriatic acid, has discovered that frogs suffocated in the oxygenated muriatic acid gas exhibit a very high degree of irritability after their death.

I beg you will fix the attention of Mr.

Vauquelin on the action of sulphate of pot-ash upon the nerves.

I have been astonished at every thing I beheld.

Two legs of frogs in a very lively state were steeped in the solution of the sulphate of pot-ash. I tried them three or four minutes afterwards with the metals.

The contractions had increased in force, and were even convulsive.

It appeared that the three acidifiable bases contained in the solution hydrogene, azote, and sulphur, acted strongly on the oxygene conveyed by the arterial blood.

This action revives the process of vitality.

After fourteen or sixteen minutes the whole thigh became of a blackish brown.

All the oxygene of the blood was absorbed, and the carburet of hydrogene appeared in a disengaged state.

The zinc and the silver are not then capable of exciting the smallest motion.

Yet it would be a great mistake to conclude that all irritability is exhausted in this case.

I have seen the contractions re-appear several times on restoring oxygene to the fibre by means of a solution of the oxide of arsenic.

The flame is thus renewed which seemed ready to expire.

The oxide of arsenic produces a tetanus and perfect insensibility if the nerve remains long immersed.

It seems then that the too great quantity of oxygene absorbs as it were the acidifiable bases which support the chemical process of vitality.

I have thrown the whole thigh into the solution of pot-ash, and I observed that galvanism afterwards had the power of exciting motion.

You see, Sir, what an immense number of experiments remain to be made on these objects of vital chemistry.

It is enough that a method has been pointed out of measuring the degree of irritability of the organic parts by means of galvanism.

I shall have the honour to send you my work on the nervous and muscular fibre, and on the chemical process of vitality.

I collect facts, and mistrust my own hypothetical ideas.

You will perceive with me how mistaken the notion is that oxygene performs the principal part in this process.

My experiments prove that the irritability or tone of the fibre depends only on the mutual equilibrium between all the elements of the fibre, azote, hydrogene, carbone, oxygene, sulphur, phosphorus, &c. The chemical combinations of phosphorus and of azote, for example, appear to be in no respect less important than those of oxygene with the acidifiable bases.

How much light may we not expect from the advances of yourself, Fourcroy, and Vauquelin on these objects!

Von Humboldt.

Addition to the foregoing Letter.

HAVING preserved some frogs for the winter, I have this morning repeated some experiments, of which I venture to send you an account.

In the preceding letter I have remarked that, as we are only superficially acquainted with the principles of vital chemistry, we ought not to be surprised if we do not always obtain the same results.

A negative experiment proves nothing against another of an affirmative nature.

I am very sure that a nerve rendered insensible by alcohol will not recover its irritability by sulphate of pot-ash.

But it may very well happen that a thigh, of which the tetanus has been caused by the oxide of arsenic, should remain in a state of tension notwithstanding the action of the solution of pot-ash.

I have seen the following facts within this quarter of an hour.

I took the four extremities of a very lively frog.

The right arm and the right leg leaped on zinc and silver.

I steeped them for four minutes in alcohol.

The hydrogene acted strongly on the fibre.

The toes of the foot trembled during the first minute.

Soon afterwards a total rigidity came on; the muscle became white, the blood having apparently lost its oxygene.

I replaced the arm and the leg on the zinc and silver, but there was not the slightest contraction.

I then quickly threw them into the oxygenated muriatic acid, which I had shaken strongly before it was poured out; the limbs remained in it for three minutes.

A slight tremulous motion shewed, even in the cup, that the vital forces were restored.

I replaced the arm and the leg on the metals; the contractions were again produced, not only with zinc and silver, but with zinc and iron.

Here I think is a very simple and decisive experiment.

I then changed the method in order to observe the effect.

I took the left thigh, and immersed it for nine minutes in alcohol.

It lost all irritability, and the oxygenated muriatic acid was no longer capable of restoring the vital force.

The left arm had remained untouched for fifteen or eighteen minutes.

I prepared its nerve, but it shewed only very weak and slow contractions with zinc and silver.

I threw it into alcohol.

After the first minute its irritability was increased, the galvanism acted more strongly; but after three minutes all the irritability was exhausted, and I applied in vain the remedy of oxygenated muriatic acid.

I steeped the arm in the solution of the oxide of arsenic, and it then afforded contractions, though very weak.

Here are four experiments, two of which succeeded, and in the two others the vital forces were not restored.

I think, nevertheless, that in good logic we ought to admit the affirmative experiments.

Examine the conditions, and you will see they are very different.

The left leg remained too long, nearly nine minutes, in the alcohol.

The right arm was already very weak when the experiment began.

Who can boast of reviving the dead?--If of two chemists the one should obtain oxygene gas by heating the red oxide of mercury, while the other did not obtain it, we should always believe that the apparatus of the latter was not hermetically closed.

I never saw an organ rendered insensible by alcohol which recovered its irritability by being left to itself.

It necessarily follows, therefore, that in the experiments I have ventured to relate, and of which my work contains a very great number, the oxygene of the muriatic acid must have been a principal agent. The art of medicine will be infinitely benefited if we should succeed in observing the phenomena which the several elements produce in contact with the irritable fibre.

It is proper to begin with simple combinations, and asterwards proceed to combinations of two, three, and four principles.

I have sent to the National Institute a memoir on the nature of light, and its chemical combinations.

Mr. Wedgwood pretends that the phosphorescence of calcined bodies is not altered in hydrogene and azotic gas. I think he did not purify these gases by means of phosphorus, as I did. I have seen luminous wood extinguished in the azotic and hydrogene gases.

A small quantity of oxygene, being admitted into the vessel, causes the whole of the phosphorescence to revive. I have also converted morilles (Phallus Esculentus) into a substance which resembles tallow, by means of the sulphureous acid.

I have made soap of it.

Spallanzani observed the same phenomena; and, what is more remarkable, he observed the phosphoric or shining animals ceased to emit light in the azote, hydrogene and carbonic gases, and that they emitted a light infinitely more vivid in oxygene gas than in the atmospheric air.

Chimico Esame degli Esperimenti de Goettling.

Modena, 1796.

Bayreuth, December 29, 1796.

Von Humboldt.