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||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
in: A Journal of Natural Philosophy, Chemistry, and the Arts 1 (November 1797), S. –363.
||Antiqua (mit lang-s); Auszeichnung: Kursivierung, Kapitälchen; Fußnoten mit Asterisken; Schmuck: Initialen.
I HAVE lately addreſſed ſeveral letters to Meſſrs. Dolomieu and Fourcroy at Paris, andperceive 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 ofthe National Inſtitute. Be pleaſed to accept my aſſurances of the great reſpect which yourzeal 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 calculatedto promote their reſearches.
You are probably acquainted with my Eſſays on the Vegetable Philoſophy, ſuch as my
Aphoriſmi ex doctrinâ phyſiologiæ chimicæ plantarum, annexed to my Flora ſubterranea Fri-bergenſis, and ſeveral memoirs which I have preſented to the National Inſtitute.⸺Thememoir on the action of oxygenated muriatic acid upon the vegetable and animal fibre,which is printed in the Magazin Encyclopédique of Millin, Noël, and Warens, ſeems to have
|360| 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 NationalInſtitute related principally to the germination of vegetables, I have thought it my duty toannounce to you certain facts more ſtriking reſpecting the animal fibre. The ſtrongeſtſtimulus of the nervous fibre is that of the alkalis. It appears that theſe ſalts affect the irritableand ſenſible ſyſtem by means of their azote. Let the thigh of a frog be thrown into theoxygenated muriatic acid, or the nitric acid, and it will remain motionleſs. Let it be putinto a ſolution of pot-aſh, or of ſoda, and it will undergo contractions no leſs ſtrong thanwhen 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 nervebe very ſenſible (for nothing more is required than ſimply to immerſe the extremity of thecrural nerve in the oleum tartari per deliquium), the contractions will end in an univerſaltenſion or rigidity. The leg riſes up perpendicularly, the membrane of the feet extendsitſelf, and the tetanus appears. In this ſituation all the irritability of the fibre appears tobe extinguiſhed; and if an electric ſtroke be paſſed through the limb, the exhauſtion becomesreal. It is a ſtriking phenomenon to ſee the laſt remaining ſigns of tetanus diſappear inan inſtant. But there is another method by which the tenſion diſappears, and by which Iam able to reſtore the irritability to the organs. It ſeems that the acidifiable baſes of thealkali, principally the azote, have conſumed all the oxygene contained in the fibre. Thechemical proceſs of vitality ceaſes. If I pour an acid, for example the nitric acid, uponthe nerve, an efferveſcence will take place; part of the alkali becomes latent, and the reſtwill have a proper proportion with reſpect to its oxygene. From this moment the con-traction with zinc and ſilver is again produced. Increaſe the quantity of acid, and themovements are again weakened. In this manner it is, that by forming an equilibrium be-tween the azote of the alkali and the oxygene of the acid applied to the animal fibre, theirritability 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 degreeof inſenſibility to which the nerve is reduced by repeating them may be very different. Itis poſſible to determine exactly the quality of the chemical agents, their weight and tempera-ture; notwithſtanding which, many experiments do not ſucceed. The reaſon is, that thereare conditions which depend on the individuality of the organization, and concerning whichwe muſt ſtill confeſs our total ignorance. The influences of the oxygenated muriatic acidupon the animal fibre are leſs marked than thoſe of the alkalis; but they are nevertheleſsof 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 al-cohol. 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 ſecondgave very ſtrong contractions, and ſhewed that its irritability was reſtored. The commonacids depreſs the irritability of the nervous fibre. A crural nerve, rendered inſenſible bythe 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 themuſcular 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, agree-able to the diverſity of the elements. The terrible action which the alkalis exerciſe on the
|361| nerves appears to explain the effect of the ſecretion of the ſeminal liquor on the blood. Itis this alkali which, diſtributed throughout the ſyſtem, anſwers the purpoſe of a ſtimulusbeneficial 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 ſilverto the mouth and the brain of a dead fiſh; it afforded no motion. I poured oxygenatedmuriatic 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 thismovement with regularity when I threw it into the oxygenated muriatic acid. The ſameexperiment ſucceeded very often with the hearts of frogs: when a heart is immerſed in aſolution of pot-aſh, it loſes its irritability for ever; ſo that azote is not the ſpecific ſtimulusof the heart.
Mr. Pfaff, while employed in my experiments reſpecting germination in the oxygenatedmuriatic acid, has diſcovered that frogs ſuffocated in the oxygenated muriatic acid gasexhibit a very high degree of irritability after their death. I beg you will fix the attentionof Mr. Vauquelin on the action of ſulphate of pot-aſh upon the nerves. I have been aſto-niſhed at every thing I beheld. Two legs of frogs in a very lively ſtate were ſteeped inthe ſolution of the ſulphate of pot-aſh. I tried them three or four minutes afterwardswith the metals. The contractions had increaſed in force, and were even convulſive. It ap-peared that the three acidifiable baſes contained in the ſolution hydrogene, azote, and ſul-phur, acted ſtrongly on the oxygene conveyed by the arterial blood. This action revivesthe proceſs of vitality. After fourteen or ſixteen minutes the whole thigh became of ablackiſh brown. All the oxygene of the blood was abſorbed, and the carburet of hydrogeneappeared in a diſengaged ſtate. The zinc and the ſilver are not then capable of excitingthe 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 bymeans of a ſolution of the oxide of arſenic. The flame is thus renewed which ſeemedready to expire. The oxide of arſenic produces a tetanus and perfect inſenſibility if thenerve remains long immerſed. It ſeems then that the too great quantity of oxygene abſorbsas it were the acidifiable baſes which ſupport the chemical proceſs of vitality. I havethrown the whole thigh into the ſolution of pot-aſh, and I obſerved that galvaniſm after-wards had the power of exciting motion.
You ſee, Sir, what an immenſe number of experiments remain to be made on theſe ob-jects of vital chemiſtry. It is enough that a method has been pointed out of meaſuringthe degree of irritability of the organic parts by means of galvaniſm. I ſhall have thehonour to ſend you my work on the nervous and muſcular fibre, and on the chemical pro-ceſs of vitality. I collect facts, and miſtruſt my own hypothetical ideas. You will perceivewith 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 mutualequilibrium between all the elements of the fibre, azote, hydrogene, carbone, oxygene,ſulphur, phoſphorus, &c. The chemical combinations of phoſphorus and of azote, forexample, appear to be in no reſpect leſs important than thoſe of oxygene with the acidi-fiable baſes. How much light may we not expect from the advances of yourſelf, Four-croy, and Vauquelin on theſe objects!
A Letter from Mr. Von Humboldt to M. H.
on the Chemical Proceſs of Vitality;together with the Extract of a Letter from Citizen
on theſame Subject
HAVING preſerved ſome frogs for the winter, I have this morning repeated ſome ex-periments, of which I venture to ſend you an account. In the preceding letter I have re-marked 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 ex-periment proves nothing againſt another of an affirmative nature.
I am very ſure that a nerve rendered inſenſible by alcohol will not recover its irritabilityby ſulphate of pot-aſh. But it may very well happen that a thigh, of which the tetanus hasbeen cauſed by the oxide of arſenic, ſhould remain in a ſtate of tenſion notwithſtanding theaction of the ſolution of pot-aſh.
I have ſeen the following facts within this quarter of an hour. I took the four extremi-ties of a very lively frog. The right arm and the right leg leaped on zinc and ſilver. Iſteeped 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 rigiditycame on; the muſcle became white, the blood having apparently loſt its oxygene. I re-placed 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 ſtronglybefore it was poured out; the limbs remained in it for three minutes. A ſlight tremulousmotion ſhewed, even in the cup, that the vital forces were reſtored. I replaced the arm andthe leg on the metals; the contractions were again produced, not only with zinc andſilver, but with zinc and iron.
Here I think is a very ſimple and deciſive experiment. I then changed the method inorder to obſerve the effect. I took the left thigh, and immerſed it for nine minutes inalcohol. It loſt all irritability, and the oxygenated muriatic acid was no longer capable ofreſtoring the vital force. The left arm had remained untouched for fifteen or eighteenminutes. I prepared its nerve, but it ſhewed only very weak and ſlow contractions withzinc 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 theſolution 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 forceswere not reſtored. I think, nevertheleſs, that in good logic we ought to admit the affirm-ative experiments. Examine the conditions, and you will ſee they are very different. Theleft leg remained too long, nearly nine minutes, in the alcohol. The right arm was al-ready very weak when the experiment began. Who can boaſt of reviving the dead?—Ifof 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 thelatter was not hermetically cloſed. I never ſaw an organ rendered inſenſible by alcoholwhich recovered its irritability by being left to itſelf. It neceſſarily follows, therefore, thatin the experiments I have ventured to relate, and of which my work contains a very greatnumber, the oxygene of the muriatic acid muſt have been a principal agent. The art ofmedicine will be infinitely benefited if we ſhould ſucceed in obſerving the phenomenawhich the ſeveral elements produce in contact with the irritable fibre. It is proper to begin
|363| with ſimple combinations, and aſterwards proceed to combinations of two, three, and fourprinciples.
I have ſent to the National Inſtitute a memoir on the nature of light, and its chemicalcombinations. Mr. Wedgwood pretends that the phoſphoreſcence of calcined bodies isnot altered in hydrogene and azotic gas. I think he did not purify theſe gaſes by meansof phoſphorus, as I did. I have ſeen luminous wood extinguiſhed in the azotic and hydro-gene gaſes. A ſmall quantity of oxygene, being admitted into the veſſel, cauſes the whole ofthe phoſphoreſcence to revive. I have alſo converted morilles (Phallus Eſculentus) intoa ſubſtance which reſembles tallow, by means of the ſulphureous acid. I have made ſoapof it.
Bayreuth, December 29, 1796.
Addition to the foregoing Letter.