Timothy 0. Lipman Horvard University Cambridge, Mossochusetts
Wohler's Preparation of Urea and the Fate of Vitalism
i n 1828 Friedrich Wohler announced the discovery of the artificial preparation of urea from inorganic compounds. Some H t y years later judgment had been passed upon the preparation: "No single chemical discovery of this century haa exercised so great an influence in the development of scientific thought"(1). Another writer hailed the preparation as an "ever memorable" experiment, since it "removed a t a single blow the artificial barrier which had been raised A between organic and inorganic chemistry"($). relatively modern reconstruction of Wohler's experiment has attempted to recreate the excitement engendered by the discovery: Wohler was excited. He was standing upon the threshold of a new era in chemistry, witnessing "the great tragedy of science, He had the slaying of a beautiful hypothesis by an ugly fact!' synthesmed the first organic compound outside the living body. The pregnmt mind of young Wijhler almost reeled a t the thought of the virgin fields rich in mighty harvests which now awaited It was indeed a brilliant new the creatures of the crucible. day for chemistry (3).
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These statements characterize the view that WWler's investigation completely eliminated the vitalistic concept of organic chemistry, that the laws governing the organic world were seen to be no different from those governing the inorganic world. Such opinions would no longer be accepted as historically accurate. Organic chemistry as we know it was not established immediately with the single preparation of urea. There is, however, no concurrence of opinion among historians concerning the place of Wohler's work in the history of scientific thought. To what extent, for example, did thepreparation of urea alter chemical thought? What were the effects of the discovery upon vitalistic thought? In the attempt to answer these questions, a controversy has arisen which ranges from high praise of Wohler's work as a major achievement to denial of the discovery as having any importance a t the time. On the one side, W. H. W a m n (4a)believes that the discovery was received as a work of importance to the future of organic chemistry, that its signikance with respect to vitalistic thought was recognized by contemporary scientists. On the other hand, Douglas McKie (6) asserts that the historical importance of Wohler's discovery has been inkted beyond all proper proportions and that the synthetic preparation of urea is a myth of chemical history. There was no synthesis of an organic comThis paper was prepared at Harvard University with the aid of a NSF grant GE 1258 (Undergraduate Science Education) under the direction of Everett Mendelsohn. I am also indebted to Harry Burstyn, Uta Merzbach, Wade Chambers, and Judith Pound far their encouragement and suggestions.
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pound from inorganic matter, nor did Wohler himself believe he had truly synthesized organic material. McKie states that there was no diminution of a belief in vitalism among the chemists of the time; rather, the function of a vital force in the formation of organic substances continued to be asserted. On Warren's side of the controversy, Ernest Campaigne (6) believes that the evidence shows Wohler to be the first to clearly "record and comment on the synthesis of an orgsnic substance from materials known to be inorganic. . . (6). Campaigne supports Warren's position that the significance of the preparation was noted by the important chemists of the day. There is thus a need for reevaluation of the importance of Wohler's experiment in the development of scientific thought. I n order to clarify the relation of Wohler's work to vitalism and to the development of organic chemistry, the basic tenets of vitalistic thought will be reviewed. The nature of W6hler1s discovery, his own views concerning its significance, and its reception among contemporaries, will then be investigated. We can then establish the significance of the preparation of urea for the growth of scientific ideas in the nineteenth century. The Concept of Vitolism
Vitalistic thought, like the phlogiston theory or the aether concept, had no rigorous format, but there were general principles common to most expressions of vitalism. Basic was the belief in an impassible gulf between the organic and inorganic worlds. For example, the French physiologist Xavier Bichat believed that the gulf was partially reflected in the high degree of variability and instability found in the vital properties. This instability of the vitrtl pOWeI8, this disposition which they continually have to change, impresses upon all the physiological phenomena a character of irregularity which particularly diatinguiahes them from those of physics. The latter forever the same, are well known when once they have been analysed; but who e m say that he k n o w the former, because he has analysed them under the same circumstances, a multitude of times. The urine, indeed, the saliva, or the bile indifferently taken from such or such B subject, may be analysed, and hence reaults our animal chemistry; hut such s chemistry is the dead anatomy of the fluids, not a physiological chemistry (7a).
For Bichat, living bodies possessed a "permanent principle of reaction" (7b) which countered the inorganic influences tending to destroy the organized body. The phenomenon of life itself was the opposition of the vital forces within the organism to the inorganic forces without the organism. L i e was maintained because the vital forces opposed the ordinary chemical forces which were attempting to reduce the organism to
its inorganic elements. According to this view of vitalism, inorganic and organic chemistry were governed by not merely diierent, but rather opposing forces. Another example of vitalistic thought is John Webster's "Manual of Chemistry," (8a)' the chemistry textbook used a t Harvard University in the years prior to Wohler's preparation. Webster stated that organic bodies were composed of four inorganic elements, yet knowledge of the components was not sufficient for an understanding of the organic substances. I n the mannfacture and functioning of living bodies there was involved a "directing principle," which pertained only to organized bodies and was superior to and different from the normal cause of chemical reactions. There were thus two operating forces in the chemical worldchemical affinity and vital power. Chemical a5nity was the motivating cause of all inorganic chemical reactions. As such it was available to, and used by, the chemist in his laboratory. On the other hand, vital power was the motivating force behind all actions in the organic world. This force was not available t o the chemist nor would it ever be, for the chemist could never imitate nature in her organic synthetic operations. In short, the vitalistic view held that there could never he made in the laboratory a substance whose existence was dependent upon the vital force of living organisms. Wohler's Interpretations of His Discovery
It is against this background of two worlds of chemistry that Wohler2 published the results of his investigations (9). The paper is short and unexciting. There is little to differentiate it from any of the several hundred other papers he published during his career. Wohler stated that in 1824 he had found that one of the products of a reaction of cyanogen (C2N2) with ammonia solution was a "crystallizable white suhstance." He had determined that the product was not ammonium cyamte. In 1828 the same substance was obtained from a reaction of ammonia with cyanic acid (HNCO). Through the performance of various tests, Wohler further concluded that the substance was neither an ammonium nor a cyanate salt. The thought then occurred, Wohler continued, that perhaps an organic substance had been produced. He therefore experimented with the substance and found that it reacted with nitric acid in a manner identical to urea. This similarity induced him to conduct parallel experiments with pure urea isolated from urine. He reached 1 Although this is s n American textbook and hence might be thought of a s not the equal of s Continental textbook, it has "Mmual of Chemistry" gives the been observed that the " reader greet respect for its author, on account of its clarity of Three appresentation, excellent style, m d modernity. pendices, called 'Addenda,' show the extent t~ which Webster kept up with the latest developments in science!' Cohen, I. Bernard, "Some Early Tools of American Science," Cambridge, Massachusetts, Harvrtrd Univ. Press, 1950, p. 93. ' The question arises of whether W6hler himself was a vitalist. Any answer given can only he an educated guess because there is little discussion of vitalism by WBhler. Nonetheless, it is most likely that he was a vitalist. He was a student and follower of the vitalist Berzelius, and there is no evidence that Wohler questioned or rejected the views of his teacher. In addition, since the accepted st& of organic chemistry was vitalistic, it is reasonable to assume that Wohler remained within the scheme of knowledge and thus believed in the existence of a separate vital power which governed the formation of organic bodies.
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the unexpected conclusion that the crystalline substance and urea were without a doubt identical materials. Of course, we would most like to know how Wohler reaarded his own discoverv. Unfortumtelv for the historian, W6hler wrote little about his experLent with urea, and the shortness and simplicity of the paper i b self leave unanswered important questions. How is it, for instance, that the thought of the possible forrnation of an organic compound occurred to him a t all? That is, if the gulf between inorganic chemistry and organic chemistry was as great as we indicated, why did he think of something which had been considered impossible? Why did he not comment upon the achievement of the impossible? Or does the lack of comment indicate that Wohler had no conception of the implications of his discovery? I n his paper Wohler mentioned the relation of his experiment to vitalistic thought only once, and rather indirectly a t that, stating that here was ". . . a n example of the artificial formation of an organic, indeed a socalled animal substance, from inorganic materials" (9a). Wohler thus dismissed in one sentence a discovery that threatened to overthrow a major conceptual scheme of the period. He appeared more interested in the properties of isomerism that were observed; that is, two compounds totally diierent in their chemical properties-urea, and ammonium cyanate--were composed of the same elements in the same proportions.
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I abstain from all the speculations which so naturally present themselves in consequence of these facts, especially concerning the combining proportions of organic compounds, concerning the identical elementary and qualitative composition of com. (9a). pounds of very different properties
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One wonders why the more strikmg fact that he had prepared an animal compound, formerly thought obtainable only by means of the action of the vital forces, did not seem worthy of some speculation. However, it cannot be said that Wohler was unexcited about the fact that he had artiicially made an organic substance. I n a letter written to the chemist Berzelius shortly after the discovery, Wiihler said that he would not wait for an answer to his last letter because "I cannot, so to speak, hold my chemical water . . . (10). He continued that he could make urea without the necessity of a kidney or an animal, be it a man or a dog. This was not the statement of one who doubted the actuality of the change from inorganic to organic. Furthermore, his haste indicated that he thought the discovery important. At the end of the letter Wohler wrote several sentences that are open t o varying interpretation: This sstificial formation of urea, can one regard it as an example of the formation of an organic substance from inorganic matter? It is striking that one must have for the production of cyanic acid (and also of ammonia) always a t the start an organic substance, and a nature philosopher would say that the organic [powerla has not yet disappeared from either the animal carbon or the oyanic compounds derived therefrom and m organic body may always be brought from it (IOa).
It has been asserted by McKie that in speaking of a nature philosopher, Wohler was refering to himself and a
The German reads "das Organische!' Volume 41, Number 8, August 1964
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thus did not believe that he had formed an organic substance from inorganic origins. Most likely, however, Wohler was not talking about himself in the above sentences. It is the only point in the letter in which he used the third person; there was no reason for him to switch to an impersonal form a t the end of a personal letter. If he had had doubts, he would have continued to use ich. Furthermore, he stated without question in two other places that he had produced an animal sub~ t a n c e . ~It is possible that Wohler was refering to any scientist who might have made an objection to the validity of the preparation. That is, the German Naturphilosoph might be taken as meaning "natural philosopher." However, this is not likely as the t e r n "natural philosopher" in reference to a scientist was not in common use in the nineteenth century. It is most probable that Wohler's nature philosopher was a member of the romantic movement, Naturphizosophie. The Naturphilosoph believed that all creation was but a manifestation of the World Spirit. Although all matter was possessed with spirit, organized bodies were the highest on a developmental scale and thus manifested the spirit most actively. I n this philosophy the preparation of urea would be nothing more than an increased activation of spirit already present. It is important to note that Wohler was not discussing vitalism but rather predicting the objections that might be raised by the Naturphilosoph. Naturphilosophie was not the same as vitalism, and a comment of Wohler toward the former has little relevance to our discussion of the latter (11). Wohler thus did not doubt that he had prepared an animal substance. He was, indeed, quite excited and most anxious t o relate the details of his experiment to his former teachcr. Wohler saw possible objections to the discovery, but these were not his own. However, although Wohler believed he had formed an animal substance, this does not necessarily mean that he believed he had bridged the gap between the inorganic and organic worlds. His excitement did not generate any questioning of vitalistic doctrine, and his lack of discussion about the implications of his discovery for vitalism would indicate he thought there were none. As there is no evidence to indicate anything to the contrary, we are led to conclude that Wchler remained a vitalist after the discovery. Views of Wohler's Contemporaries
The reaction of Wohler's contemporaries presents much the same problem as that of Wohler himself. It was generally recognized that Wohler had made an important discovery. There was little, if any, attempt to prove that the substances with which Wohler worked were in reality organic. Few claims were made that organic spirits were dormant in the material used. Rather, the facts were accepted and acknowledged, and Wohler was praised for his artificial formation of urea. Yet there was little diminution in the belief in vitalism. There developed the paradox that the artificial formation of an orgauic compound did not affect the theory that it was impossible to construct an organic compound in the laboratory. In 1828, after WRhler's publication, John Webster's
"Manual of Chemistry" (8b) which we mentioned earlier as a Harvard textbook, was revised to include all new developments in the science of chemistry. In an extensive footnote under the section discussing urea, Webster gave the full details of Wdhler's paper as an additional means of obtaining pure urea (8b). Nonetheless, this footnote did not affect the author's belief in vitalism. The opening pages on vegetable chemistry in which he outlined the general principles of the action of vital forces remained unchanged. One might think that there was not sufficient time for complete revision before publication. However, this edition was used at Harvard through the 18301s, and there was no change in the statement that nature would not be imitated in her vital powers. The preparation of urea was t,hought important enough to be included in the text, most likely causing the printer some difficulty. Yet there was no change in Webster's vitalistic thought after this new development. Berrelius
The reaction of the confirmed vitalist Berzelius is somewhat more complicated than that of Webster; there is little doubt that he regarded his former pupil's discovery as being important. I n reply to the letter in which Wohler informed h i of the discovery, Berzelius termed it an "important and beautiful" ( l o b ) discovery, and said it gave him indescribable pleasure to hear of it. I n a later letter commenting on Wohler's narrow miss of the discovery of vanadium, he said that a man who had prepared an organic substance from inorganic material could be forgiven for not having discovered a new element (4b). Although in each of these letters he had his tongue-in-cheek part of the time, he seemed to regard the discovery as important. However, the praise was somewhat tempered. In reply to Wohler's letter telling of the discovery, Berzelius devoted only one paragraph for cougratulations. He then urged Wohler not to abandon his researches on beryllium and yttrium: However, do not for anything in the world give up the reduction of beryllium earth and yttrium earth, after which I yearn to the highest [extent] and so much that, it it did not appear that I wanted to graze my cow in the pasture of the Herr Doctor, I would have given Magnus a small sample of grsdolinite to set right to work on the reduction of yttrium earth (IOc).
The effect is as if Berzelius had said: "yes, the preparation of urea is very interesting, but do not waste too much time with it a t the expense of accomplishing some thing more important." Moreover, a t no point does Berzelius acclaim the discovery as bsidging the gap between two areas of chemistry. The error has been made that praise of the discovery was given with the understanding that the preparation seriously undermined the doctrines of vitalism.' An example of a misinterpreted laudation is the repost of the discovery by Beraelius in JahresRericht: One of the most unexpected and therefore most interesting discoveries in the area of animal chemistry is unquestionably the artificial formation at urea. This discovery was made by Wiihler (12).
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' I n his p q x r and at the beginning of the letter
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Warren makes this error of interpretation throughout his paper.
important, such praise does not necessarily reveal any change in vitalistic outlook. Only if the statement were used t o corroborate other indications of a change in view could it be taken to express an altered attitude toward vitalism. A mere compilation of "unexpected"~and interesting"^ is not sufficient ground to indicate that a new direction for chemistry was recognized a t the time. Berzelius did think the discovery important because it was another in a growing list of the examples of isomerism (13). He was most explicit here as he was not in other ways: Thin fact holds the key to many clearer views, and shows, that with the same number of simple atoms distributed in a dissimilar manner among themselves in the larger molecule, the creation of bodies with different properties is possible, as we already have begun to experience through other examples, whose reliability, however, must yet be strengthened through other similar examples (id).
It will be remembered that Wohler felt isomerism was the phenomenon of significance upon which to speculate. An interest in isomerism is not surprising. In 1823 Wohler had analyzed cyanic acid and in the following year Liebig had analyzed fulrninic acid. The analyses were found to be identical, much to the general astonishment of the chemical community. By 1827 Berzelius had stated that there was no mistake, and that two substances with identical elementary composition could have different properties. Slowly it was realized that structure was as important in organic chemistry as composition. Since this was a most difficult concept to grasp, it was natural that excitement would be generated when another example was discovered. Such an example was urea. Hence, while Berzelius congratulated Wohler on the preparation of urea from inorganic material, he was far more interested in the preparation as a new example of isomerism. Furthermore, Berzelius never abandoned vitalistic theory. The first sentence of the section on organic chemistry in his textbook published in 1847 read: "In the living nature the elements seem to obey entirely different laws than they do in the dead . . ." (14). The essence of a living body was not bound in its inorganic elements; rather, the essence was beyond the normal qualities of the inorganic elements, e.g., hardness and electrical polarity. The inorganic elements of an organic body could not be destroyed, but the particular nature of the body could be destroyed. An organized body that gave up its contents to the inorganic world could not be recreated as could an inorganic compound. Wohler's artificial preparation of an organic substance did not alter Berzelius from the ways of vitalism. Johonnes MGller
Another of Wohler's contemporaries who maintained the vitalistic principles was Johannes Miiller. His "Elements of Physiology" discussed explicitly the differences between organic and inorganic chemistry. Organic bodies had "proximate principles" which were peculiar to them. These bodies could be analyzed, but they could not be produced by any chemical process. Organic compounds also had a tendency to decompose, and only the continuity of life prevented decomposition. I n the cessation of l i e organic matter was annihilated and fell under the laws which regulated inorganic chemical compounds.
Chemical compounds, we know, are regulated by the intrinsic properties and the elective affinity of the substances uniting to form them; in organic bodies, on the contrary, the power which induces and maintains the power of their elements does not consist in the intrinsic properties of these elements, but something else, which not only counteracts their affinities, hut effects opers, tions conformably to laws of its own operation (16a).
Admitting that recently there had been some doubt as to the possibility of constructing organic compounds in the laboratory, there was still much to favor denial of such a view. Berard, Proust, Dobereiner, and Hatchett believe, indeed, that they have succeeded in producing organic compounds by artificial processes, but their results have not been sufficiently confirmed. Wohler's experiments afford the only trustworthy instances of the artificial formation of these substances; as in his procuring urea and oxalic acid artificially. Urea, however, can scarcely be considered a4 organic matter, being rather an excretion than a comnonent of the animal bodv. In the mode of combination of it's elements it has not perhaps the characteristic properties of organic bodies (16b).
This was not the discussion of one who bad rejected the notion that there was a difference in the laws governing the organic and inorganic worlds. Since the "Elements of Physiology" was a standard and widely used textbook, we can conclude with reasonable assurance that Miiller's views toward organic chemistry and Wohler were not unpopular. Justus Liebig is of interest in that he represented somewhat of a transition firmre with resnect to vitalism. That is, he felt organic ccemistry wa's quite close to inorganic chemistry. For instance, in 1837 the British Association for the Advancement of Science published a communication from Liebig relating the progress of his work with Wohler on the decomposition products of uric acid. I n the paper Liebig appeared well aware of the new direction taken by organic chemistry. Unlike Berzelius and Miiller, there was greater recognition that organic chemistry was not a science unique unto itself. I t may be affirmed with the utmost certainty, that urea and uric acid are products of the organization, We cannot discover their existence in any part of our food, nor do they constitute a part of any organ, as fibrin does of the blood, hut they are chemical combinations of a peculiar nature, on which account they come more within the range of chemical investigation than [The] extraordinary, and any other bodies of animal origin. to some extent inexplicable, production of this substance without the assistance of the vital functions, for which we are indebted to Wohler, must be considered one of the discoveries with which a new era in science has commenced ( 1 6 ) . There are many bodies similar to urea all of which will probably, at a future period, be produced by artificial means (1'3).
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I n addition, in the joint publication with Wohler of the results of the uric acid experiments, a similar idea was expressed: The philosophy of chemistry will draw the conclusion from this work that the production of all organic substances, as long as they no longer belong to the organism, must be considered not merely as possible within our laboratories, but rather as certain. Sugar, salicin, morphine will be prepared artificially. We do not yet know the way to reach this end result, because the [necessary] antecedents, from which these substances develop, are unknown to us, but we will learn them (17).
Hence, Liebig appeared to have recognized the new Volume
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nature of organic chemistry indicated by the preparation of urea. Nonetheless, Liebig remained a vitalist. His vitalism differed from that of Berzelius and Muller. It was somewhat more sophisticated, and there was more understanding of the relation between inorganic and organic chemistry. He admitted that chemical action was the source of mechanical power in organized bodies. Only the chemical force was capable of connecting the patiicles of two dissimilar elements and uniting them into a compound. The same laws were found in organic nature, and the elements in both animal and vegetable organisms were in the same 6xed and immutable c o m b i i g proportions. However, Liebig did not reject the validity of the concept of vital force. It was not to be used in the same sense as electrical or magnetic force; but it was, Liebig continued, a collective term,
. . . embracing all those causes on which the vital properties depend. In this sense it is as just, and may he used with as much propriety, and convey a similar meaning to the tern "force of afity" or "chemical force" which denotes the cause of chemical phenomena, of which we know quite as little as we do of the cause or causes which determine the vital phenomena (18a). For Liebig the vital force influenced the number of atoms which united, and it governed their arrangement within the molecule. It could change, elevate, d i s h or annihiiate the chemical force. There were chemical forces withim the organized body, but it was incorrect to conclude that all the forces within the organism were those that governed inorganic matter. The vital force hss not the slightest influence upon the combination of the simple elements, as such, into chemical compounds. No element, by itself, is capable of serving for the nutrition and development of any part of an animal or vegetable orgmism. All those substances which take part in the processes of life are inferior groups of simple atoms, which, under the iuBueuoe of the vital force, combine into atoms of a higher order. The chemical force, under the dominion of heat, determines the form and properties of all the more simple groups of atoms, whilst the vital force determines the farms and properties of the higher order of atoms, that is, of organic atoms (186).
Even Liebig, therefore, retained the belief in a separate force which governed the organic world and diferentiated it from the inorganic world. Nineteenth Century Scientific Though1
Quite obviously the strikmg example of the artiiicial preparation of urea from inorganic materials did not eliminate vitalistic thought. What seems to be a brilliant refutation of a theory no longer accepted was, in effect,ignored. It had been repeatedly stated that it was impossible to make an organic substance in the laboratory. Wo'hler did just this. The question, then, to be answered is why did the preparation of organic from inorganic have so little apparent effect on scientific thought? Muller had claimed that urea, being an excretion, was not a component of an organized body and therefore not a true organic compound. Similarly, the French chemist Gerhardt asserted that urea should be classified with carbon dioxide and water, both substances found in the organized body, but not organic in themselves (5). However, urea had not been classified previously with carbon dioxide and water. In Webster's first edition of "Manual of Chemistry," 456
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urea had been discussed under animal chemistry, and carbon dioxide had been discussed under compounds of inorganic carbon. Furthermore, Liebig had asserted that urea was an organic compound formed by the body. Obviously, a new classification was a mere stopgap attempt to deny the results of the experiments. Such methods in themselves would not have had the force to negate the new direction in which the discovery is said to have turned organic chemistry. To deny that urea was organic is not a sufficient answer to the question of why the preparation did not immediately alter scientific thought. McKie has objected that the reactants used by Wohler were not dead, inorganic substances, so that there was no preparation of the organic from the inorganic. The preparation may have been without a kidney or a dog, states McKie, but not without dried blood, horns, or hoofs. It was a "mere item of code'' to regard the starting materials as inorganic; Wohler performed a transformation, not a synthesis. The fads are true, but the objections are invalid. As reported by Webster's "Manual of Chemistry," cyanogen was prepared chiefly from the red oxide of mercury and Prussian blue. The Prussian blue was obtained from various animal parts such as the dried blood, hoofs, and horns. However, this does not mean that there were thought to be undestroyed organic qualities in the Prussian blue and in the cyanogen. Webster stated that in the process of decomposition, the animal matter resolved into a variety of inorganic products arising from the reunion of the ultimate parts of the animal matter. The preparation of cyanogen md, from that, cyanic acid, was described in the section of the text concerned with inorganic chemistry and inorganic carbon. There was no mention of the preparation of any cyanide product in the sections on animal and vegetable chemistry. There was no doubt that cyanogen and cyanic acid were inorganic bodies, and it was not thought that Wohler had released powers residmg in the elements. The starting materials were completely dead. Moreover, the assumption that there were dormant organic qualities would have contradicted basic principles of vitalistic thought. While the Naturphilosoph would object that the preparation was an activation of organic spirits withm the elements, this would not be a vitalistic objection to Wohler's discovery. For the vitalist there were no qualities peculiar to the certain elements contained in organic compounds. It was recognized that the organic world was made of the same elements that were in the inorganic world. It was not thought that in the few elements composing organic bodies there were innate powers which could appear under certain conditions to make the compound organic and then could disappear into the element. Rather, it was thought that there were two dierent kinds of forces governing the e l e ments. When the force of chemical a w t y dominated, it was the inorganic world. When the vital force acted to unite the elements in a certain complex way, this constituted the organic world. The distinction was between two forces in a world of one type of element, not two types of elements obeying one force. Much of the difficulty comes from the application of a modern conceptual scheme to a dierent period of
history. Science today does not accept a vitalistic theory of organic chemistry. When a thread of evidence which supports our own concepts is seen, it is easy to wonder why another age did not realize the importance of this set of facts. Only in relation to the scientific thought of the time can the reception of Wohler's work be understood. While the chemistry of the inorganic world in the early nineteenth century was inorganic chemistry, that of the organic world was animal and vegetable chemistry, not organic chemistry. Animal aud vegetable chemistry was not concerned with the chemistry of carbon, but rather with the phenomenon of life. How certain substances composed of elements from the inorganic world could exhibit growth and self-maintenance was the question to be answered. It was not denied that complex carbon compounds could be made. No one thought to deny it because it was not the topic of concern. Rather, it was denied that life could be created by the action of the force of chemical afFnity because a single force could not explain the manifest diierences between the living and the dead worlds. Only the vital forces could create lie. Since these vital forces were not available for use by man, the chemist could never create the organic world in the laboratory. I n short, the chemist could not create life. "Organized Bodies" not "Organic Substances"
The vitalistic point of view arose because science was engaged in an attempt to explain organized bodies, not organic substances. The distinction between organic bodies and organized bodies was subtle but real. There was no life in organic bodies as there was in organized bodies; there was no life in urea or sugar as there was in an amoeba or a dog. Organic bodies formed organized hodies, and organized bodies constituted the living organic world. There was no need for a vital force to explain nonliving, organic substances; there was, on the other hand, need for a vital force to explain the creation of a living, organized substance. In this context the artificial preparation of urea was almost insignificant, as would have been any similar preparation. The only formation of importance would have been the synthesis of liie, that is, the trausformation from the organic to the organized. To produce an animal substance was not t o produce a living substance. That someone had artificially prepared urea did not explain, nor did it suggest any explanation to, the differences between the living and the dead worlds. Since the production did not answer the problem of life, it did not necessitate the questioning of vitalistic thought. It would have been most surprising if the artificial preparation in itself had caused the overthrow of vitalism. W i l e vitalism was not eliminated after Wohler's discovery, it underwent change during the first half of the nineteenth century. It is readily apparent that the vitalism of Liebig was not the vitalism of Bichat. Bichat questioned the constancy and stability of any vital phenomenon. Liebig did not question that, given constant conditions, determinate phenomena would result. Nonetheless, Liebig felt that the creation of the more complex molecules constructing the organized body was under the influence of a vital force, not the force of chemical afIinity. Vitalistic thought
had attempted to explain both the creation and rnaintenance of lie. Alteration was inevitable because of expanding chemical knowledge. With the development of more proficient analytical techniques (19) and with the impetus given by WBhler's discovery as the first of more to come, the explanation of the maintenance of liie increasingly came in chemical terms. With the contraction of the region of the unknown because of the establishment of the chemical nature of the maintenance of life, vitalism by the middle of the century was reduced to an attempt to explain the creation of life. Vitalism disappeared from science as a major force only when the attempt to explain the transformation from organic to organized was abandoned. Rather than become further involved in an effort to understand this transformation, the l i e sciences were compartmentalized into the more rigidly defined areas of organic chemistry and physiology. The former treated the organic bodies only, and the latter treated the organized functions, omitting the question of the creation of life. The chemist's assault upon the organized body as the focal point in the quest for an explanation of the l i between the organic and the organized had necessitated the establishment of a vital force to explain this link. When chemistry shifted its focus, when the chemist could say we will no longer ask questions about the origins of organized bodies, vitalistic ideas no longer influenced chemical thought. Gradually, knowledge gained from the study of the organic bodies answered the questions formerly asked about the organized bodies. The explanations were achieved, however, after they were no longer sought. Summary
Wohler's preparation in itself neither changed chemistry nor overthrew vitalistic doctrine. I t was part of a massing of evidence which changed vitalistic thought. Ultimately vitalism diappeared with the emergenceof anewset of questions. Something thought to be impossible was seen not to he; theory had to be expanded to account for the new phenomenon; and the answers to the first questions produced new questions. The shift from a doctrine of vital forces to a unsed scheme of chemistry was a function of time and factual accumulation. The significance of the artificial preparation of urea is that it was a major element in the long accumulation of evidence which eventually necessitated a unified scheme of chemistry. Litemture Cited (1) THORPE, T. E., "Essays in Historical Chemistry," 2nd ed., London, MacMillan and Co., 1902, p. 302. (2) HOFMANN, A. W., "The Feraday Lecture far 1875; The Life Work of Liebig in Experimental and Philosophic Chemistry," London, MacMillan and Co., 1876, p. 22; A. W.. Bey. Deut. Chem. Ges.. 15. 3127 (1882). HOFMANN. (3) JAFFE,BERNARD,"Cruoibles: the ~ i v &.&d chie evemen* oC Llle Great Charrrists," New York, Newton Publishing Co., 1932, pp. 177-8. (4) (a) WARREN, W. H., THIS JOURNAL, 5, 1539 (1928); ( b ) The report of the letter can also be found in HOFXANN, A. W., Ber. Deut. Chem. Ges., 15,3171 (1882). N a t u ~ e 153, , 608 (1944). (5) MCKIE,DOUGLAS, (6) CAMPAIGNE, ERNBST, THIS JOURNAL, 32, 403 (1955). (7)' BICHAT.X A ~ I E R"Phvsioloeical . Researohen on Life m d ~ e a t h , "translated dy F. GOLD,Boston, Richardson and Lord, 1827, (a) pp. 78-9; ( b ) p. 10. Volume 4 1 , Number 8, August 1 9 6 4
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(8) WEBSTER, JOHN W., "A Manual of Chemistry on the Basis
of Profemor Brande's," Boston, Richardson and Lord, ( a ) 1826; (b) 1828. (9) WOHLER,FRIEDRICH, "On the Artificid Formation of Urea," translated by GOLDBLATT, L. A,, "Rea,ding~in Elernentary Organic Chemistry," New York and London, 1938, pp. 11-12 as found in ( a ) GUERLAC, HENRY,"Selected Readings in the History of Science," 1953, Vol. 2, part 2, pp. 4 7 2 4 ; (6) Original paper: WORLER,F., Ann. Pogg., 12,253 (1828). (10) WALUCH,0."Briefweehsel zwischen J. Berzelius und F. Wbhler," Leipaig, Wilhelm Engelmann, 1901, Val. 1, (a) p. 206; ( b ) p. 208; ( c ) p. 209. (11) For a discussion on Naturphilasophie: Mason, S. F., "Main Currents of Scientific Thought," New York, Henry Schumm, 1953; O E E S ~ DHANS , CHRISTIAN, "The Soul in Nature," tramlsted by LEONORA AND JOANNA HORNER, London, Henry G. Bohn, 1852; STAUF PER, R O B E ~C., T Isis, 48, 33 (1957).
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(12) BERZELIUS,JACOB, translated by F. W ~ L E R Jahres, Rer. Fortsch. physischen Wissen., 9, 266 (1829). (13) PARTINGT:TON, J. R., "A Short History of Chemistry," 3rd ed., New York, Harper and Brothers, 1960, pp. 203-4 for a diaeuaaion of iaomerism. (14) BERZELIUS, J. J., "Lehrbuch der Chemie," Dreaden and Leipzig, Arnoldischen Buehhandlung, 1847, Vol. 4, p. 1. (15) MBLLER,JOHANNES, "Elements of Physiology," translated
by WILLIAMBALY,Philadelphia, Lea and Blanchmd, 184.3, (a) p. 16; (6) p. 15. Rep. Selrenth Meeting B ~ i t .Assoc. Advan. (16) LIEBIG,JUSTUS, Sn'.; Notes and Abstracts, 7,38 (1837). (17) W~~ELEE, I?., AND LIEBIG, . J., . Ann. Phamack.. 26, 242
(1838): (18) L I E B I ~JUSTUS, , "Familiar Letters on Chemistry," 4th ed., London, Walton and Maberly, 1859, (a) p. 193; lbin.201. ~ (19) HOLMES, FREDERIC L., Isis, 54. 50 (1963) for a complete discussion of organic analysis.
