Bert, Paul

(b. Auxerre, France, 19 October 1833; d Hanoi, Indochina [now People’s Republic of Vietnam], 11 November 1886)

physiology, comparative anatomy, natural history, education.

Bert was the son of Joseph Bert, lawyer and conseiller de préfecture of the Department of Yonne, and of Jeanne Henriette Massy, who was of Scottish extraction on her father’s side, He attended the elementary school and the Collège Amyot at Auxerre from 1843 to 1852. In 1853 he went to Paris, where he studied jurisprudence and obtained the licentiate in law. He studied medicine and science from 1857 to 1866, receiving the licentiate in natural sciencesin 1860 and the M.D., with a thesis on animal transplantation, in 1863. From 1863 to 1866 Bert was the student and préparateur of Claude Bernard at the Collège de France. In 1866 he was awarded the doctorate in natural sciences with the thesis De la vitalité propre des tissus animaux. In 1865 he married Josephina Clayton, a Scotswoman.

Bert was professor of zoology and physiology at the Faculté des Sciences of the University of Bordeaux in 1866–1867. In 1868 he replaced Flourens (as suppléant) in the chair of comparative physiology at the Muséum d’Histoire Naturelle, and the following year he succeeded Claude Bernard in the chair of physiology at the Sorbonne.

Bert was a member of the Société des Sciences Historiques et Naturelles de l’Yonne, the Société Philomathique de Paris, the Société de Biologie de Paris, and the Académie des Sciences de Paris.

The Franco-Prussian War caused Bert to enterpolitics. After the capitulation of the French Imperial Army at Sedan in September 1870 and the resignation of Napoleon III, Bert joined the forces led by the Government of National Defense, whose driving force was Léon Gambetta, who was also his personal friend. The following January he became Préfet du Nord and organized a hopeless resistance. After the war, Bert joined the Liberal Republican party and was elected in 1872 to the Chamber of Deputies. His political aims were regeneration and revanche. The recovery of the lost eastern provinces, Alsace and Lorraine.

The means of political, economic, industrial, intellectual, and moral regeneration was, for him, a radical reform of education at all levels, and particularly of the elementary schools. As a deputy, as chairman of important parliamentary committees, and as minister of public instruction (from 14 November 1881 to 26 January 1882) he fought for enactment of the laws proposed by Jules Ferry a well-known liberal politician and influential minister of public instruction. In a masterful report on elementary education presented to the Chamber of Deputies, Bert explained Ferry’s principles. He demanded free, compulsory elementary schooling, with a secular program and lay personnel. The schoolteacher must not belong to the clergy. He is the soldier of the secular republic.

The program of the elementary school must include the elements of science, for the sciences sharpen the intellect: the natural sciences develop the power of observation, and the physical sciences sow the seeds of causal thinking. History and paleontology will reveal the gradual development of man from a cave dweller to a culture-bearing, free, republican citizen; thus evolution, and not revolution, will be man’s guiding principle. The “Ferry laws” were enacted between 1880 and 1886.

Bert supported secondary education for girls. For many years he lectured at the Sorbonne on biology and zoology to girls aged sixteen to eighteen. Bert also published elementary and secondary textbooks on natural history, zoology, and the physical sciences. These books, which show his remarkable didactic Ability, were reprinted many times and translated into English, Italian, and Spanish. It was Bert’s firm belief that the principles of science should pervade the whole of society in order to make it better. The Revues scientifiques, a periodical that he edited from 1879 to 1885, bears witness to Bert’s endeavor to popularize science.

In 1885 the French people were alternately enraged and perplexed by the revolts in Indochina against the new French colonial regime. In the stormy debates in the National Assembly, Bert sternly defended the French colonial expansion in Indochina. Appointed as the first civil governor of Annam and Tonkin in 1886, Bert sought a true partnership between France and Indochina. He eliminated the military interference in administration and “pacified” the areas he governed. In Annam he strengthened the power of the emperor, and in Tonkin he relied on popular forces, which he strengthened by political and social reforms. In addition, he established the Tonkin Academy and founded numerous schools.

In 1855, when still a law student, Bert became a member of the Socièté des Sciences Historiques et Naturelles de l’Yonne. This marked the beginning of his research. Bert’s scientific thought and method were later shaped by three eminent scientists who taught him: Pierre Gratiolet Henri Milne-Edwards, and Claude Bernard. He studied with Gratiolet in the laboratory of comparative anatomy at the Museum d’Histoire Naturelle in Paris. There he learned that within the great variety of structures “the problem of life was but one.” Bert was also deeply influenced by Milne-Edwards’ Introduction to General Zoology (1851). This book revealed to him how nature worked through “the law of economy,” the “division of labor,” and the perfection of functions by means of specialization. It was to Claude Bernard, however, that Bert owed his greatest debt. As a student and collaborator of Bernard, he became acquainted with the methods of experimental physiology, the critical evaluation of experimental findings, and the attempt to describe the basic laws of physiology. Bert was deeply impressed by Bernard’s concept of an internal environment.

Bert’s scientific activity can be divided into three periods: (1) In the 1860’s—as a student of medicine and science, as préparateur for Bernard, and as professor of zoology and comparative physiology at Bordeaux and Paris—he dealt with questions of general Physiology, plant physiology, and comparative anatomy and physiology. During that period he published important monographs on animal transplantation and the vitality of tissues, and a comprehensive study on the comparative physiology of respiration. (2) After the Franco-Prussian War, he published his magnum opus, La pression barométrique (1878). (3) A last period of scientific activity, which was a direct offshoot of his barometric work, dealt with the experimental and clinical study of anesthesia and with the properties of blood at high altitude.

Through all his scientific work we can perceive the constant endeavor to study the phenomena of life in the context of the exterior and interior environment.

Bert’s first important work dealt with animal transplantation. This study was not intended to be a contribution to experimental surgery, for transplantation was conceived of as a physiological problem: How can transplanted organs and tissues live in a New environment? Bert succeeded in creating “double monsters.”, uniting two rats by suturing their skins together. He also implanted the tip of the tail of a young albino rat under the skin of its back; the proximal end of the tail was then cut, so that it formed the tip of the grafted tail. The transplanted tail grew, formed new bone, and reestablished circulation and sensibility-but the direction of the sensory impulse was reversed.

Bert’s investigation of the specific vitality of animal tissues was a pure environmental study. He used the transplantation technique as a means of examining the vital resistance of organs and tissues. Isolated tails of rats were exposed to different temperatures and humidities, and to various gases and chemical agents. After these exposures the tails were transplanted under the skins of rats. The transplantation reestablished a physiological internal milieu and made it possible to test the survival of the tail tissues after they had been subjected to various changes of environment. Bert emphasized that the cells and tissues lived their own lives, growing and differentiating independently of any superior vital force as long as they were in a suitable milieu.

During his professorship at Bordeaux, Bert dealt with problems of marine biology and plant physiology. He studied the mechanism of death in marine fishes exposed to fresh water, and he observed the occurrence of Amphioxus lanceolatus on the south-western coast of France. He also published his classic study on the movements of the “sensitive plant” (Mimosa pudica). Using ether, he succeeded in differentiating spontaneous movements from induced ones. The spontaneous movements depended on differences of osmotic pressure, which was regulated by light and darkness.

In 1870 Bert published an important work dealing with problems of the comparative physiology of respiration. This monograph was based on his lectures delivered at the Muséum d’Histoire Naturelle, Paris, in the spring semester of 1868. Bert analyzed the anatomical structures and the physiological functions of the respiratory organs of vertebrates and invertebrates. He also dealt with the problem of tissue respiration and showed that the oxygen content of the blood depended on the exterior air pressure. The respiratory movements of aquatic and air-breathing animals were investigated with novel methods and techniques. He studied the nervous regulation of the respiratory rhythm and investigated the respiration of diving animals. He analyzed the death mechanism of asphyxia and succeeded in clearly differentiating true asphyxia caused by lack of oxygen from carbondioxide poisoning. This work, rich in facts and new views, also provided a critical evaluation of a vastnumber of problems.

Bert’s definitive work, La pression barométrique, published in 1878, represented an environmental study on the largest scale. The great questions were How does the changing exterior milieu—the atmospheric Pressure—act on an organism? What are the effects of low pressure at high altitudes? How does the high pressure to which the caisson worker is exposed affect the body? How does the blood, the interior milieu, behave under high and low pressures? What is the mechanism of mountain sickness? Bert’s interest in these problems arose early in his scientific work. In 1864, while a student of Bernard, he had discussed the question of whether the amount of gases dissolved in the blood depended on atmospheric pressure. The French physician Denis Jourdanet, who had practiced in Mexico and was interested in the biological and medical aspects of high-altitude climates, provided Bert with the necessary means to build the costly apparatus needed for the experimental study of the physiological effects of air pressure. Jourdanet had constructed pressure chambers for therapeutic use and had formulated the hypothesis that the blood contained less oxygen under the low atmospheric pressure of high altitudes, a condition he called barometric anoxemia.

In his first series of experiments Bert studied the following problem: What extremes of air pressure can a living being endure? He first examined the effects of low pressure and found that animals died after the partial pressure of oxygen sank below a critical level that was constant for each species. Bert therefore announced the following principle: Oxygen tension is everything; barometric pressure in itself does nothing or almost nothing.

Bert then studied the physiological effects of pure oxygen or air inhaled under high pressure: the dogs used died with tonoclonic cramps. Thus he discovered the phenomenon of acute oxygen poisoning and was able to state that if the organism receives too little oxygen, it suffocates; and if it is exposed to oxygen at high pressure, it is poisoned. In a second series of experiments he studied the behavior of blood gases under various pressures. These investigations relied on the fundamental studies of blood gases made by Carl Ludwig and his students. Bert found: “The combination of oxygen with hemoglobin is likely to be partially destroyed, to be dissociated at low pressures…. Everything seems to indicate that there exists in the neighborhood of normal pressure a point of chemical saturation of the oxyhemoglobin, and that beyond this point there is added to the blood only oxygen dissolved in the serum according to Dalton’s law.”

Bert also experimented on himself in the pressure chamber in order to study the effects of low atmospheric pressure on the human body. When the pressure was decreased to 400 millimeters of mercury, he noted increased pulse rate, headache, dizziness, darkening of the vision, mental lassitude, and nausea. These complaints disappeared as soon as he inhaled oxygen. Bert also trained balloonists in his pressure chamber and provided them with oxygen bags for their flights to high altitudes. He recognized that when the partial pressure of oxygen is reduced, the altitude sickness of the aviator, the mountain sickness of the alpinist, and the complaints encountered in lowpressure experiments appear. Bert also clarified experimentally the mechanism of decompression sickness (caisson disease). Sudden decompression from high atmospheric pressures (five-ten atmospheres) produced gas bubbles in the blood and tissues. These gas bubbles consisted primarily of nitrogen that had previously been dissolved under high pressure and was liberated by the decompression. Bert emphasized that the duration of compression was of great importance. As prophylaxis for caisson disease he devised a slow, gradual decompression; treatment was recompression and low decompression.

The results of Bert’s monumental work were manifoldfold: He fully realized the physiological importance of the partial pressures of the respiratory gases. He described the relationship between the external partial pressure and the behavior of the blood gases. He recognized that mountain sickness and altitude sickness are a consequence of the low partial pressure of oxygen. He introduced oxygen apparatus to avert the dangerous consequences of ascent to high altitudes. He was the first to study in a pressure chamber the conditions of high-altitude ascents. He discovered and described oxygen poisoning, and explained the cause and mechanism of caisson disease.

Bert applied his knowledge of the physiological effects of atmospheric pressure to the field of anesthesia. He reasoned that the pressure at which nitrous oxide induces anesthesia is about one atmosphere. Therefore pure nitrous oxide has to be used, but it induces asphyxia. To avoid this, Bert prepared a mixture of one-sixth oxygen and five-sixths nitrous oxide. He administered this mixture to dogs under the slightly increased pressure of 1⅕ atmospheres. Thus the blood was supplied with enough oxygen to sustain life and enough nitrous oxide to produce anesthesia. Bert went on to the application of this method to clinical anesthesia, constructing a horsedrawn anesthetic chamber in which the surgeon, his assistants, and the patient could be placed underslightly increased pressure.

In La pression barométrique Bert discussed the problem of acclimatization to high altitudes. Is the blood of individuals at high altitudes capable of absorbing more oxygen than the blood of individuals living at sea level? Three possibilities might be conceived: a qualitative change in the hemoglobin, an increase in the hemoglobin content of the red corpuscles, or an increase in the number of erythrocytes. Starting from Bert’s hypothesis that people living at high altitudes might possess more red corpuscles, François Viault examined human and animal blood in the Peruvian Andes from 1890 to 1892. He observed on himself and on his companions that the number of erythrocytes increased from 5,000,000 to 7,000,000 within three to five weeks. This important fact, which showed a substantial change of what is normally a biological constant, initiated the systematic high-altitude research in the Alps (conducted by Hugo Kronecker, A. Mosso, and others).

As a true disciple of Bernard, Bert hailed the emergence of physiology as an exact scientific discipline. He refused to adhere to any dogmatic materialism. He emphasized that the cerebral function was indispensable for the production of psychic phenomena. But organized matter could not be the only Cause, the sufficient condition, for intellectual manifestations, for this would mean transcending the realm of scientific physiology. Outside of physiology, he believed, remained the immense field of subjective phenomena that cannot be investigated with the methods of physiology.

BIBLIOGRAPHY

I. Original Works. Bert’s scientific works include “De la greffe animale,” M.D. thesis (Paris, 1863); Recherches experimentales pour servir à l’histoire de la vitalité propre des tissus animaux, Ph.D. thesis (1866), pub. in Annales des sciences naturelles (Zoologie), 5 (Paris, 1866), 123–218; “Recherches sur les mouvements de la sensitive (Mimosapudica, Linn.),” in Mémoires de la Société des Sciences Physiques et Naturelles de Bordeaux, 4 (1866), 11–46, also published separately (Paris, 1867); Leçons sur la physiologie comparée de la respiration… (Paris, 1870); Recherches expérimentales sur l’influence que les modifications dans la pression barométrique exercent sur les phénomènes de la vie (Paris, 1873); “Sur la possibilité d’obtenir, à l’aide du protoxyde d’azote, une insensibilité de longue durée, et sur l’innocuité de cet anesthésique,” in Comptes rendus hebdomadaires de l’Académie des Sciences (Paris), 87 (1878), 728–730; La pression barométrique, recherches de physiologie expérimentale (Paris, 1878), his masterpiece, trans. into English by M. A. Hitchcock and F. A. Hitchcock as Barometric Pressure. Researches in Experimental Physiology (Columbus, Ohio, 1943); “Anesthésie par le protoxyde d’azote mélangé d’oxygène et employé sous pression,” in Comptes rendus hebdomadaires de l’Académie des Sciences (Paris), 89 (1879), 132–135; Leçons de zoologie… (Paris, 1881); Leçons, discours et conférences (Paris, 1881), Which includes political and educational papers as well as scientific ones; La première année d’enseignement scientifique, sciences naturelles et physiques: animaux, végétaux, pierres et terrains, physique, chimie, physiologie végétale (Paris, 1882), trans. by Josephina Clayton (his wife) as First Year of Scientific Knowledge (Paris, 1885).

II. Secondary Literature. Works on Bert are E. H. Ackerknecht, “Paul Bert’s Triumph,” in Bulletin of the History of Medicine, supp. 3 (1944), 16–31, which treats Bert’s place in French intellectual history and includes an important bibliography; E. Bérinon, L’oeuvre scientifique de Paul Bert (Paris, 1887); C. A. Culotta, “A History of Respiratory Theory: Lavoisier to Paul Bert, 1777–1880,” thesis (Univ. of Wisconsin, 1968), which includes a detailed discussion of Bert’s work on blood gases; L. Dubreuil, Paul Bert (Paris, 1935), comprehensive biography with special emphasis on Bert’s political importance; J. Ducloz, “L’enfance et la jeunesse de Paul Bert,” in Bulletin de la Société des Sciences Historiques et Naturelles de l’Yonne, 78 (1924), 5–102; and N. Mani, “Paul Bert als Politiker, Pädagog und Begründer der Höhenphysiologie,” in Gesnerus, 23 (1966), 109–116.

Nikolaus Mani