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Jacob Moleschott
(9 Aug 1822 - 20 May 1893)

Dutch physiologist and philosopher noted for his belief in the material basis of emotion and thought. For example, he recognized phosphoric lime is mined, used to fertilize his wheat, which nourishes not only the body, but also the human brain. Thus “No thought without phosphorus!”


By Prof. E. P. EVANS.

from Appleton's Popular Science Monthly (1896)

[p.399] THE distinguished physiologist, Jacob Moleschott, was born August 9, 1822, in Hertogenbush,1 the capital city and chief commercial and industrial center of North Brabant in Holland. His father was a physician of some note, and his paternal grandfather a reputable apothecary; on his mother’s side he was the grandchild of the celebrated Dr. Van der Monde. His mother was a woman of superior culture and refinement, and she and her more sedate and scientific husband devoted themselves with conscientious care and excellent discretion to the early education of their child.

The Moleschotts were originally Catholics. In 1797 the grandfather’s dwelling, together with his large apothecary shop and storehouse, which contained a hundred thousand florins’ worth of Peruvian bark and other medicaments of great value, was’ burned to the ground, thus reducing him at once from a state of affluence to extreme poverty. Not one of the many priests, who had constantly enjoyed his generous hospitality, lifted a finger to help him in his distress. A few prominent Protestant citizens came to his aid, and by their timely efforts enabled him to resume his business, which he carried on with such success as partially to retrieve his fortune, so that when he died in 1838 he was a comparatively wealthy man. The unsympathetic conduct of his coreligionists made a deep impression upon him as well as upon his son, who was then a child, and instead of pursuing his studies at the Catholic seminary at Warmond, he entered the University of Leyden, to which he was especially attracted by the eminent humanist, Prof. Daniel Wyttenbach, a man as conspicuous for learning as for breadth and freedom of thought. The influence exerted by this liberal thinker and scholar was wholesome and permanent, and decisive in determining the future intellectual character of the Moleschott family.

In his fifteenth year Jacob Moleschott was sent to the Prussian gymnasium at Cleves, not far from the Netherlands frontier, where he remained five years. He was then matriculated as a student of medicine and natural science in the University of Heidelberg.

At the solicitation of Nägele, Moleschott prepared a dissertation on a pathological problem which had been already discussed by the professor, but which could be definitely solved only by the [p.400] aid of the microscope. The difficult task was performed to the entire satisfaction of Nägele, who took occasion to express it in a peculiar manner. As Moleschott was returning for the first time from clinical practice in the lying-in hospital, for which he had paid the required fee to the secretary, Nägele accompanied him, and, as they were going downstairs, stuck the amount of the fee into Moleschott’s vest pocket with the remark, “Clericus clericum non decimat (Clergy does not take tithes of clergy).”

In 1844 the Teyler Society of Harlem offered a prize for the best dissertation on Liebig’s theory of the nutrition of plants, which formed the basis of his application of chemistry to agriculture, and which at that time excited as lively discussion in the scientific world as did Darwin’s theory of the origin and evolution of species fifteen years later. Moleschott took a deep interest in the subject and was urged by Delffs to compete for the prize, which was also awarded to him. His dissertation contained a thorough examination and keen analysis of Liebig’s views, and pointed out some instances of hasty generalizations and unwarranted conclusions. Moleschott exposed these logical fallacies and showed how largely they entered into the reasoning and vitiated the deductions of the distinguished chemist. The copy of the prize essay sent to Liebig was accompanied by a note in which Moleschott, while venturing to criticise his views, expressed the warmest admiration and enthusiasm for his personal character and scientific achievement. Liebig replied, thanking him for the essay, and added: “So far from being offended by opposition, I desire it, since it serves to separate the grain from the chaff”; and I have all the more reason to be satisfied when this is done, as in your case, in a clever and gentlemanly manner.

On January 22, 1845, Moleschott passed his examination, and was promoted to the degree of Doctor of Medicine, receiving the first rank. But in order to practice his profession in Holland it was necessary to have a certificate of proficiency also from a Dutch university. For this purpose he went to Leyden, where he passed the so-called colloquium doctum, which consisted in a pleasant conversation with professors of the medical faculty—Broers, Pruys van der Hoeven, and Suringar—on the endemic diseases of Holland. He then established himself in Utrecht.

In connection with Donders and a Jewish physician. Van Deen (afterward professor in the University of Groningen), Moleschott founded a scientific journal for the publication of the latest researches made by Hollanders in anatomy and physiology, to which Mulder, Harting, Jansen, Van den Broek, Kees Verloren, Eduard von Baumhauer, and others sent valuable contributions. Notwithstanding the congeniality of many of his associations and his interest in these investigations, he was not contented with his life and [p.401] prospects in Utrecht. One day a Protestant clergyman paid him a visit and, after speaking in flattering terms of his professional ability and success, expressed regret that Moleschott did not attend church, and promised, on this condition, to recommend him to the members of the congregation. Moleschott thanked him for his good opinion and kind intention, but positively declined to pretend to worship God in the service of Mammon.

Moleschott’s predilection for scientific research became more and more a passion to him. He determined henceforth to make a specialty of the study and teaching of biology in the broadest sense of the terra as the science of life, and for this purpose habilitated as Privatdocent in his alma mater, the University of Heidelberg. No sooner was his intention made known than he was offered the position of Lecturer on Medical Jurisprudence in the University of Utrecht, which, however, had no attractions for him.

The subject chosen for his first course of lectures at Heidelberg in the summer of 1847 was physiological chemistry, and, although his audience was small, it comprised a number of students who afterward became scientists of distinction. As the fees for lectures furnished only a scanty source of revenue, he was compelled to keep up a limited medical practice and to devote himself earnestly to literary work. One of his first tasks of this kind was a thorough revision of the volume on foods in Prof. Tiedemann’s elaborately planned but unfortunately never completed Manual of Human Physiology, which he undertook at the request of the venerable author.

On March 14, 1849, Moleschott married Sophie Strecker, the eldest daughter of a prominent citizen of Mayence, who entered heartily and intelligently into her husband’s special studies and proved to be an efficient helpmate in catching and preparing frogs for experimental purposes, and aiding him in his microscopical observations.

In a course of lectures on the blood and its constitution, especially as to the effects of different kinds of food upon the relation of the white to the red corpuscles, Moleschott was assisted by seven students, who volunteered to undergo the necessary experiments. They came in the morning without having eaten anything and then partook of the prescribed diet, whose nutritive qualities were to be tested by an analysis of the blood. If eggs and other albuminous fare, roast meats, and peas were served, all was well; but if the meal consisted merely of potatoes and apple sauce, the youthful votaries of science, after their work was done, returned to their homes with ravenous appetites and pillaged cupboards and kitchens, so that the cooks in their respective families began to gossip about the queer sort of hospitality shown by that Dr. Moleschott, who invited the young men to dine with him and [p.402] insisted that they should come with empty stomachs, and then sent them home as hungry as wolves. About this time he also succeeded in demonstrating that frogs exhale more carbonic acid in the light than in the dark, thus proving that light accelerates the processes of assimilation in animal organisms, and that, too, independently of the temperature of the environment or the motion of the animal.

Meanwhile he had prepared and published his Lehre der Nahrungsmittel (Erlangen: Enke, 1850). This work, of less than two hundred and fifty pages, written “für das Volk,” and admirably adapted to convey popular information concerning the digestive qualities and nutritive properties of common articles of food, was favorably received, and in a few years passed through three editions. It presented in a clear and concise manner the results of researches embodied in his Physiologie der Nahrungsmittel, issued a few months earlier and intended for physicians and naturalists, and was translated into Dutch, English, French, Italian, Spanish, and Russian. It is divided into three principal parts, the first of which treats of the general metamorphosis of matter in living organisms, the origin and formation of the blood and of the solids in the human body, the processes of assimilation, segregation, and excretion as the conditions of growth, and the physiological nature of hunger and thirst as sensations which inform the brain through the medium of the nerves that the blood is being impoverished. In the second part he shows how this impoverishment is checked and the waste repaired by nutriment, of which the various kinds—meat, eggs, bread, cake, peas, beans, lentils, potatoes, beets, cabbage, and other vegetables, and different sorts of fruit—are discussed as to their alimentary functions and value. We then have a chapter on drinks—water, milk, tea, coffee, chocolate, beer, wine, and brandy—and another on spices, or rather on condiments, in which are included not only salt, pepper, mustard, ginger, and other spices, but also butter, olive oil, vinegar, sugar, and cheese. In the third part there are rules of diet in their application to man as a not strictly omnivorous, but largely multivorous microcosm, with remarks on breakfast, dinner, and supper, nutriment for infancy, youth, middle life, and old age, for women, workmen, artists, scholars, and other persons of sedentary habits, and the different sorts of food suitable for summer and winter. All these points are discussed in a series of short sections with a perspicacity and perspicuity and power of condensation rarely combined in scientific treatises. This feature of the work was especially praised by Alexander von Humboldt.

Perhaps even a greater sensation than by the book itself was made by a long review of it in a Leipsic weekly journal (Blätter für literarische Unterhaltung, November 9, 1850), by Ludwig [p.403] Feuerbach, who summed up its teachings in the pithy phrase, “Der Mensch ist was er isst” (“Man is what he eats”). A similar utterance is that with which Moleschott closes the chapter on the nutritive properties of leguminous plants: “Ohne Phosphor, kein Gedanke” (“Without phosphorus no thought”).

Moleschott’s book had a socialistic as well as a scientific character, although this feature was hardly recognized by his contemporaries and critics. It indicated the direction which European legislation is now taking to solve the social question, namely, through the stomach, by making better and surer provision for the present and future wants of the working classes.

About eighteen months later Moleschott published his Physiologie des Stoffwechsels in Pflanzen und Thieren (Erlangen: Enke, 1851), of which Humboldt, in a letter dated November 30, 1851, expressed his warm appreciation and hearty indorsement. This work, however, was only preliminary to another of wider scope, entitled Der Kreislauf des Lebens: Physiologische Antworten auf Liebig’s chemische Briefe (Mainz: Zabern, 1853; fifth edition, 1887), consisting of a series of twenty letters on revelation and natural law, with strictures on Liebig’s confusion of these conceptions, the sources of human knowledge, the eternity of matter, its gradual evolution, constant circulation, and endless transformations in the growth, decay, and renewal of animal and vegetable life; force as an. essential and inseparable quality of matter, especially as regards the functions of the brain in their relations to the faculty of thought and the freedom of the will, and kindred topics.2

In the practical application of his theories Moleschott animadverted on the prevailing custom of burying the dead in permanent cemeteries, where their bodies decay with no advantage, and often with serious injury, to the living. “If every place of burial,” he says, “after having been used a year, should be exchanged for a new one, it would become in the course of six or ten years a most fertile field which would do more honor to the dead than mounds and monuments.” But, he adds, it would be still better if we could return to the ancient custom of burning the dead, which he declares to be unquestionably more practical as well as more poetical. By this process the air would be made richer in carbonic acid and ammonia, and the ashes, which contain the elements of new crops of cereals for the nurture of man and beast, would transform our barren heaths into luxuriant plains. At present, he adds, we are acting like the stupid and slothful servant who buried his one talent in the earth instead of wisely investing it so as to gain another.

[p.404] These views, while commending themselves to naturalists like Humboldt, Donders, Van Deen, Emil Rossmässler, Otto Ule, and Hermann Burmeister, and scholars like Strauss and Renan, gave great offense not only to the orthodox clergy but also to conservatives of every sort, to whom the cremation of the human body seemed as sacrilegious as its dissection did to the contemporaries of Vesalius three centuries before. As the result of a solemn conclave held by the senate of the Heidelberg University, the rector of that institution warned Moleschott that, unless he ceased to corrupt youth by his “immoral” and “frivolous” teachings, the venia docendi, or right to lecture, would be revoked. The sole fitting answer to such an ill-advised and impertinent admonition was given at once by Moleschott, who wrote to the Baden ministry severing his connection with a university in which liberty of instruction existed only in name. This decisive step was evidently an unpleasant surprise to those who had provoked it, and thereby raised a storm of indignation in scientific circles and in the press which they were wholly unprepared to meet. The young men who had just attended Moleschott’s courses of lectures on anthropology and organology published with their several signatures an address to the ministry, in which they vigorously repelled these accusations and vindicated Moleschott’s character as a man and teacher. In their daily intercourse with him they declared that they had never detected the slightest justification of the charges brought against him. In the communication of the results of his scientific researches there was not the faintest trace of the spirit of proselytism, but every one was left free to form an independent judgment in accordance with the facts.

Although no longer an academical teacher, Moleschott continued to reside in Heidelberg, working in his private laboratory, to which he also freely admitted all who wished to make experiments under his direction, and keeping his head financially above water by literary labor. Thanks to his calumniators, public attention was called to his books, and the sale of them greatly increased. He also founded a scientific journal entitled Untersuchungen zur Naturlehre des Menschen und der Thiere, which began to appear in 1855 at irregular intervals, and numbered among its contributors some of the most distinguished European men of science. Moleschott edited the first fifteen volumes of this periodical, or yearbook, as it might more properly be called; since 1892 it has been continued by G. Colasanti and S. Fesbini (Giessen: Emil Roth). He also published an exceedingly interesting monograph, Georg Forster,der Naturforscher des Volkes, issued November 20, 185-4, on the hundredth anniversary of the birth of this most remarkable man.

In the spring of 1856 Moleschott was appointed to the chair of Physiology in the University of Zurich as the successor of Karl [p.405] Ludwig, who had been called to Vienna. On June 21st of the same year he delivered his introductory lecture, the subject of which was Light and Life. It was printed as a pamphlet, which went through three editions. On his way to the lecture room he met the rector of the university, Hermann Köchly, who was not only an acute philologist but also something of a wag, and who assured him that the peasants, led by their pastors and armed with clubs, were coming down the lake to put a stop to such godless proceedings, just as a dozen years before they had overthrown the government that ventured to offer a professorship to David Strauss.

At that time the society of Zurich was uncommonly attractive, owing in a great measure to the presence of many political refugees from France, Germany, and Italy, whom the reaction which followed the Revolution of 1848 had driven into exile. Very pleasant, too, and stimulating were his associations with G. H. Lewes and George Eliot, who came to Zurich on purpose to visit him; with Varnhagen von Ense, Gottfried Keller, Princess Wittgenstein, Countess d’Agoult, and especially the geologist Eduard Desor, at whose country seat in the Jura, Combe-Varin, a select circle of congenial spirits met from time to time for the interchange of thought and the discussion of scientific questions. Among those who were wont to assemble under Desor’s hospitable roof besides Moleschott may be mentioned Carl Vogt, Charles Martin, Jacob Venedey, Liebig, Schönbein (the discoverer of guncotton). Dr. Hans Küchler (a German Catholic parson), and Theodore Parker, who spent the summer of 1859 in the Alps for the benefit of his rapidly failing health. At these meetings papers were read, and Moleschott speaks in the highest terms of one by Parker, entitled A Bumblebee’s Thoughts on the Plan and Purpose of Creation, an exceedingly acute and amusing persiflage of the anthropocentric theory of the universe. These essays form the contents of Desor’s Album of Combe-Varin, a unique memorial volume of about three hundred pages. Moleschott and Parker often differed in their ideas, but entertained the warmest regard for each other as earnest and honest seekers after truth. Curiously enough, a peculiarly strong attachment sprang up between Parker and Küchler, the radical Unitarian and the German Catholic, who used to sit for hours in conversation under an evergreen tree, a fit symbol of their lasting friendship and now known as “Parker’s Fir.”3

[p.406] In the autumn of 1861 Moleschott was called by Cavour to the chair of Physiology in the University of Turin. In 1876 he was made senator of the kingdom of Italy, and in 1879 appointed to a professorship in the newly organized University of Rome, where he united with his academical duties and senatorial functions an extensive practice as a physician. There he died, May 20, 1893; and, although more than threescore years and ten, he was constitutionally so robust that his death may be said to have been premature. Like his father, he fell a victim to overwork and exposure in the conscientious exercise of his profession. During the last twenty years of his life he devoted himself also with laudable zeal and marked success to the land of his adoption in the promotion of education and the sanitary improvement of the Italian capital and other cities of the realm.

Moleschott was not only an able and painstaking specialist but also a man of broad culture, an excellent musician, a connoisseur in art, and a keen observer and intelligent critic of all the social, political, philosophical, and theological movements of the age. Whatever concerned the progress of knowledge and the perfection of humanity enlisted his sympathies and secured his support. He was a good linguist, and wrote and spoke French, Italian, and German with rare correctness and facility. The greater part of his works were composed originally in German, which he preferred even to Dutch, his mother tongue, as a medium of literary and scientific communication; but, unlike most German authors, his style is wonderfully clear and succinct, and wholly free from the awkward involutions into which the peculiar genius of the language, its very vitality and plasticity, are apt to tempt the unwary scribe. Moleschott was saved from this fatality by his artistic sense of proportion. In his treatment of a subject he had the rare gift of knowing what to put in, what to leave out, and when to stop. He was a “full” man, in the Baconian use of the term, but was mentally too well poised to slop over. He had inherited a hasty temper, but had learned in early life to keep it under control, and this natural sensitiveness under proper discipline rendered him a most charming and sympathetic companion in his intercourse with his family and his friends. Above all, he was thoroughly honest and sincere, and never permitted personal feeling to warp his judgment; in his controversies and criticisms he was generous and just, welcomed the truth from every source, and did not show the slightest disposition to ignore or depreciate the merits and achievements of an adversary.

1 [‘S Hertogenbosch (the Duke’s Bush) was originally a hunting seat of the Dukes of Brabant; hence the name.]

2 The latest editions of Moleschott’s works, his Kleine Schriften (Minor Essays), Vorträge (Addresses), etc., are now published by Emil Roth in Giessen.

3 Moleschott’s charming autobiography, Für meine Freunde (Giessen: Emil Roth, 1894, pp. 326), gives a pleasant account of the days spent with Desor and his illustrious guests at Combe-Varin. Indeed, these personal reminiscences are most delightful reading, and it is to be regretted that they have remained a fragment extending only to 1860, and thus comprising but a little more than one half of his life. The life at Combe-Varin is also described in Alfred Altherr’s Theodor Parker, in seinem Leben und Werken (St. Gallen: Wirth, 1894, ix, pp. 404). The author is the pastor of St. Leonhard’s Church in Bâle. We may add that photographs of Moleschott, of a cabinet size, may be procured from his publisher, Emil Roth, in Giessen, for one mark, or twenty-five cents.

Footnotes moved from original pages, gathered at end of page, and renumbered. Image from etching on p.288, colorization © by todayinsci, and text from E.P. Evans, 'Sketch of Jacob Moleschott', Appleton’s Popular Science Monthly (Jul 1896), 49, 399-406. (source)

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