Popular Science Monthly/Volume 73/July 1908/The Movement Towards Physiological Psychology II

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By Professor R. M. WENLEY



THIS brings us at length to the true physiological line, and to the rapid assimilation of psychology to positive science. The starting point lies in that French group whom Napoleon nicknamed contemptuously, les Idéologues: Cabanis, de Tracy, Laromiguière, and Maine de Biran.[1] Cabanis and de Tracy were the leaders in all essentials. Their movement formed part of the mighty revolutionary upheaval. By analysis of sensations and ideas they proposed to discover a method of remoulding society, government and education for practical purposes. De Tracy (1754-1836) elaborated what Beneke would have termed the "inner" side of ideology. His noteworthy efforts lie in the fields of language, grammar and logic, of economics and government, of morals and education. Yet the influence of science upon him, as upon his fellows, produced results that should receive notice here. He anticipated Comte in the view that knowledge, properly so called, consists in an organized system of the sciences; "positive science," as he declares, and to him, more than to Comte and his pupils, we owe this term, now beatified. In the second place, and coming to the physiological reference, he was the first to recognize the importance of muscular activity as a factor in consciousness.[2] This formed his point of contact with Cabanis, who studied what Beneke would have called the "outer"—the physiological accompaniments of psychological processes.

Cabanis (1757-1808) inherited the English sensational tendencies represented in France by Condillac, but he added that acquaintance with the human body which he acquired as a physician. In his person the philosophical and physiological lines coincided. His principal work, "Rapports du Physique et du Morale de l'Homme," grew out of a series of papers read before the French Institute and published in its proceedings for 1798-99. So far as he possessed any consistent philosophical standpoint, Cabanis was a pantheist (and, in speculative physiology, therefore, a vitalist), as his posthumous "Lettres sur les Causes premieres" (1824) and his discussion of the Stoics in the "Rapports" show. Nevertheless, later materialists find warrant for their most striking metaphor in his pages. As the liver secretes bile and the kidneys urine, so the brain secretes thought; thus ran Karl Vogt's raucous challenge (1847). Cabanis employed the very phrase "secretion of thought" which, as his editor, Peisse, says, "has remained celebrated." But the classical passage, also in the the "Rapports," reads as follows: "In order to arrive at a correct idea of those operations from which thought arises, we must consider the brain as a particular organ, destined specially to produce it in the same way as the stomach and the intestines are there to perform digestion, the liver to filter the bile, the parotid, maxillary and sublingual glands to prepare the salivary juice."[3] This is the clear summons to a physiological psychology. Very naturally, Cabanis aimed to supply what Condillac omitted. Condillac's sensationalism, like that of the English school, found basis in the external senses. It therefore missed those organic and internal changes which physiology alone could set forth. Cabanis, accordingly, insisted that multitudes of impressions proceed continually from the internal organs to the brain, and that the conditions of the cerebro-spinal system form a determining factor in this process. Or, to be more emphatic, as it continues to maintain its unstable equilibrium, the organism originates vital feelings within itself—feelings that bear no direct reference to the external world. That is, the impressions of Locke and Hume do not play upon a tabula rasa, but are met, and twisted, by these organic feelings. The unconscious joins up with the conscious. Of this process instinct offers a conspicuous example, Here, primordial experiences, traceable to the embryo, provide a foundation of organic sensation which (in the light of the doctrine of evolution) would explain away psychological processes as automatic—as epiphenomena of the bodily substrate. In this respect Cabanis was a prophet. Nevertheless, despite his studies of age, sex, temperament, sensibility, irritability, habit, climate, the fœtus and instinct, he fails to work through his great theme with the necessary grasp upon detail. His epoch would not let him. Yet he saw the promised land afar off. For, to him, psychology was already a natural science. It traffics with phenomena, never with metaphysical realities, and its material must be found in the relation of mental states to physiological conditions. Hampered everywhere by contemporary ignorance of nervous anatomy, he still contrived to formulate a vivid and convincing psycho-physiological schema, for which, we may as well confess, due praise has never reached him. Physiology passed to another land, and he fell into an oblivion rather discreditable to the historical insight of those who came to elaborate his anticipations.

Plainly a physiological psychology can not emerge in absence of a physiology. The numerous accessions of physiological knowledge during the last seventy years tend to obscure the unpropitious outlook at the dawn of the period. Referring to the time (1841) when he became préparateur to his distinguished predecessor, Magendie, at the Collège de France, Claude Bernard drew a gloomy picture.[4] The established "natural history" sciences—geology, botany, zoology—possessed fair equipment, particularly on the museum side. While chemistry, thanks doubtless, to Liebig's activity at Giessen, made rapid strides. But physiology enjoyed no such advantages, was opposed, indeed, even by a genius of the calibre of Cuvier. "So soon as an experimental physiologist was discovered he was denounced; he was given over to the reproaches of his neighbors and subjected to annoyances by the police."[5] Sir Charles Bell had intimated the contrasted functions of the anterior and posterior roots of the spinal nerves (1807), but had given no experimental proof: and Marshall Hall (1835) had discovered the reflex function of the spinal cord. But no group of investigators had arisen such as was to place Germany in the leadership. Her preeminence, unchallenged still for physiological psychology, dates from the life-work of Johannes Müller, and his profound influence, especially at Berlin, from 1833 till his death in the year before "The Origin of Species" (1859).

At this date the intellectual condition of Germany may be called unprecedented without exaggeration. And the fate reserved for unique things has overtaken it. Later men, particularly on the scientific side, have heaped on it multiplied misunderstanding or even obloquy. Little as I cling to them, I am compelled to declare that Schelling and Hegel were no day-dreamers, evolving camels from their inner self-consciousness. Both were great men, and Hegel takes his place among the few marvellous intellects of history. But both suffered from their very success. Hegel's philosophy formed the seedplot of that comparative and critical Wissenschaft for which human history supplies the material. As these disciplines developed, the defects of the Hegelian system became more and more irremediable. Yet, the system lacking, the sciences could not have come to birth. Schelling stood in similar case. German science from 1797, the year of the publication of his "Ideen zur einer Philosophic der Natur," till 1830 or thereby, drew inspiration from his humane, if vaulting, spirit. Alex. von Humboldt, as his biographer Bruhns points out, attempted "by means of a comprehensive collation of details, and the institution of the most searching comparisons, to give a scientific foundation to the ideal cosmology of Herder, Goethe, Schelling and their disciples." Further, Schelling stimulated Carus, the comparative anatomist: Oersted, the father of electro-magnetism; Kielmeyer, an anticipator of biogenesis; I. Döllinger, of Würzburg, who inoculated Von Baer with genetic ideas; Von Baer himself, who, more objectively than any other scientific man, has estimated the germinal significance of the Naturphilosophie; Liebig, the pioneer of laboratory methods in chemistry; Johannes Müller, the first main constructive power in modern physiology; Kieser, the early exponent of plant phytotemy; Schönlein and Röschlaub, leaders in the remarkable band who founded the Berlin school of medicine. Nay more, his power burst forth again, significantly for psychology, as a factor in the equipment of Fechner. Thus, like Hegel, Schelling paved the way for his own fall, by sending others to search out the secrets of nature. Accordingly, even if the vagaries of Oken disgusted many,[6] and if Steffens's analogies between the catastrophies of the human spirit and the disturbances of the earth's crust furnished queer geology, there were no call to "swear at large," to rush around shouting "vitalism!" or otherwise to evince complete lack of the objectivity necessary to analysis of the crisis. Somnambulists haunt the fringes of all movements, but we fool ourselves when we take them for prototypes. New ideas ever were heady; this happens to be the price set upon their power to reveal unsuspected problems, as Schelling and his galaxy of scholars did.

Johannes Möller, then, found himself born into this surging age. He tended the new scientific spirit to budding, but, unlike Von Baer, he died ere it blossomed. Speaking under reservation, as an ignorant man must, I would venture to suggest that he did not enter fully into Hegel's epoch-making idea of process. So far as I can comprehend his activity, he was a student chiefly of the organism in gross, that is, a morphologist, more than an investigator of vital processes, a physiologist. His importance lay in his ideals more than in his results. "A profound teacher," as his pupil Helmholtz declared, he created an atmosphere which his pupils breathed, and he lives in their splended work rather than in any single achievement of his own. In essentials this atmosphere contained the modern perspective. For, although, as du Bois Reymond has recorded, he "assumed the existence of a vital force. . . which in organisms acts the part of a supreme regulator," this "force" ruled the realm of the unknown only. In all that could be mastered by contemporary methods and means Müller accepted the chemico-physical view. His studies of nutrition, animal heat, motion and reflex action, his contributions to acoustics and the phenomena of speech embody, not simply his own work, they also supply a masterly unification of previous knowledge. But, especially as concerns physiological psychology, his major result undoubtedly consisted in his doctrine of "specific energies." No matter what the stimulus, the same nerve always originates the same sensation. "Müller's law of the specific energies marks an advance of the greatest importance. . . and is, in a certain sense, the empirical exposition of the theoretical discussion of Kant on the nature of the intellectual process in the human mind."[7] Of course, Müller's views drew criticism,[8] but for us now the point is that they started activity which, bit by bit, built physiological psychology into a science.

Fortunate in his disciples—Brücke, Helmholtz, du Bois Reymond, Ludwig, Czermak, Donders (most teachers would forego all personal glory gladly to obtain such human material)—Müller enjoyed luck in the contemporary course of events. For a science more developed and surer of itself than physiology was about to join forces with the newer branch. Magnus, his Berlin colleague in physics, became the focal point of a movement to which Mitscherlich, Liebig, Ohm, F. Neumann, and the brothers Weber all contributed, the first and last notably. The sobering drill of hard, experimental fact gained its recognition here. Or, as we say in philosophy, the prose of Kant was added to the romance of Schelling. For physiological psychology the steadying influence came most by way of Ernst Heinrich Weber, of Leipzig (17951878). Weber, with his younger brothers, Wilhelm and Eduard, worked from the first along distinctively modern lines. The speculative thought, prevalent in his youth, seems to have passed over his head. Exact experimental methods came naturally, as it were, to him and to his brothers. From early life they employed mechanical and mathematical analyses in dealing with physical, physiological and psychological phenomena. Kunze, Fechner's nephew and biographer, goes so far as to say, "they were among the first to raise the study of nature among Germans to the eminence occupied by the philosophers and discoveries of the Latin races."[9] Their first joint research is typical of this. In the "Wellenslehre auf Experimente begründet" they add to Chladni's acoustic theory a parallel account for light, which leads substantially to the inference of an elastic ether. Prior to this Weber had published researches on the "Comparative Anatomy of the Sympathetic Nerves" (1817) and "On the Ear and Hearing in Men and Animals" (1827). His psychological contributions appeared in Wagner's "Handwörterbuch der Physiologie," Vol. III., part 2 (1831), and in the "Archiv für anatomische Physiologie" (1835). The classical paper, "Tastsinn und Gemeingefühl," was printed in the former and published separately in 1851. Weber here applied the method of least observable differences to sensations of pressure and to the measurement of lines by the eye. These experiments resulted in the generalization to which the name "Weber's Law," or the "FechnerWeber Law," or the "Psycho-physical Law" has been given. Referring to this discovery, in the preface to the first great book on physiological psychology, Fechner affirms: "The empirical law which forms the principal foundation, was laid down long ago by different students in different branches, and was expressed with comparative generality by E. H. Weber, whom I would call the father of psycho-physics."[10] The law summarizes mathematically the relation between physiological stimulus and psychical sense-perception. It is based on the fact, familiar in common experience, and now authenticated by numerous observations and experiments, that the difference between two sensations bears no direct proportion to the actual difference between their stimuli. Granted that the least observable difference be a constant, then, the strength of sensations does not grow in proportion to stimulus, but much more slowly. Weber's experiments were directed towards measuring the exact proportions, and involved comparisons of lines by the eye, of weights and of tones. The resultant generalization has been formulated in various ways. The most direct are as follows: "In order that the intensity of a sensation may increase in arithmetical progression, the stimulus must increase in geometrical progression"; or, as put more briefly by Fechner, "the sensation increases as the logarithm of the stimulus"; or, as Delboeuf has it, "the smallest perceptible difference between two excitations of the same nature is always due to a real difference which grows proportionately to the excitations themselves." Like all laws, so-called, this one is an abstraction from experience. Consequently, it has been subjected to various interpretations, has been transformed and criticized, and even denied. Again, like all laws, so-called (e. g., Boyle's law), it holds good only within limits, and round this aspect of the matter multitudinous experiments cluster. Space forbids more than a reference to easily accessible literature.[11] Whatever psychological experts may consider to be the present status of the conclusion, Weber's withers are unwrung. His crowning achievement was to have shown that measurements and mathematical methods can be applied in this region of experience. He thus served himself the founder of the Leipzig line, the torch passing from him to Lotze, to Fechner, and finally to Wundt.

As at the beginning of modern European thought, in Descartes, Spinoza, and Leibniz, so here in the Leipzig men, philosophical insight and power were joined to scientific competence. I, therefore, leave them for a moment to take a glimpse—it can be no more—at the strictly scientific interest as we see it illustrated in Johannes Müller's greatest pupil, Helmholtz (1821-1894).

Helmholtz ranks not simply with the foremost scientific intellects of the nineteenth century but with the master minds of all time. His range, grasp and insight combined to render him monumental. A contributor to at least eight sciences—physics, physiology, mathematical physics, meteorology, medicine, chemistry, anatomy and esthetics, in three of them he stands high among the foremost. More than this, as Volkmann has recalled, "one of his chief merits was to establish a harmony between the vast accumulation of facts that characterized the period comprehending the middle of this century and the more theoretical studies."[12] Besides, he possessed unusual manipulative skill, his inventions of the ophthalmoscope and ophthalmometer alone would have assured any ordinary reputation. Above all, he was a humanist, being an accomplished musician, an art critic, and acquainted with the trend of philosophical thought. His discoveries of classical grade amaze one by their thoroughness and versatility. The conservation of energy; the mechanism of the lens of the eye in relation to accommodation; the movements of the eyeballs with the attendant problems of binocular and stereoscopic vision; the profoundest questions of hydrodynamics, thermodynamics and electrodynamics, the last culminating in the revelations of his favorite pupil, Heinrich Hertz; the axioms of geometry; the dark places of meteorology; the deeps of physiological optics and of mathematical physics, all bear witness to his profound, masculine and subtle intellect. But, for our present study, the palm must go to his long struggle with the difficulties of sensation and perception. These absorbed his principal attention from 1852 till 1867 and, in a lesser degree, till his death. He laid the foundation characteristically by his inquiries into the rate of nervous impulse in the motor and sensory nerves, about 1850, and his first paper, on sensation proper, followed in 1852. These labors were crowned magnificently by the publication, in 1863, of his "Sensations of Tone," and, in 1867, of his "Physiological Optics"—masterpieces both. The former, which involved the most complicated research, has earned the title, "the Principia of acoustics," and must be studied long to be appreciated. For, it not only ranged over the entire subject but, incidentally, raised important problems that belong elsewhere, especially to the domains of phonology and esthetics. Questions about the quality of the human voice and the absolute pitch of vowel sounds lead us away from the physical and the physiological laboratory to a very different environment. Similarly, the "Physiological Optics," with the Young-Helmholtz theory of color, presents investigations about which psychologists are bound to trouble for many a day.

Thus, the significance of Helmholtz's career may be traced to his combination of the mathematical and exact-scientific with the humanistic interest, a union to which we may attribute our greatest advances alike in science and in intellectual insight. And this fitted him rarely to execute work of abiding value for physiological psychology. No one has contrived to reach better results in those unplumbed reaches of experience where the joint action of body and mind can be studied with a measure of success. Proceeding from the theory of "specific energy" of his master Müller, he wrought it out in detail, eminently for the mechanism of sight and hearing, by experimental methods and by mathematico-physical analyses. Upon the romantic interest in nature stimulated by Schelling he superimposed the critical processes of Kant, armed with all the resources of the most delicate apparatus and rigid analytic procedure. This coalition of endowment and outlook continued in the three leaders who were destined to build psychology into an independent science—Lotze, Fechner and Wundt. To them we shall turn next.

  1. Cf "Les Ideologues," Fr. Picavet (1891).
  2. Ibid., pp. 377, 337 f.
  3. Œuvres, Vol. III., p. 159.
  4. Cf. "Physiologie générale," p. 203.
  5. Ibid., l. c.
  6. Cf. Huxley, in the "Life of Owen," Vol. II., p. 295.
  7. "Physiol. Optik.," Helmholtz, p. 249.
  8. Cf. Mind, V., pp. l ff. (old series).
  9. "Gustav Theodor Fechner (Dr. Mises): Ein deutsches Gelehrtenleben," p. 243.
  10. "Elemente der Psychophysik," preface, p. v.
  11. "German Psychology of To-day," Th. Ribot (where Delboeuf's researches are given). "The Human Mind," Sully, Vol. I.; article "Weber's Law" in the "Encyc. Britannica"; "Principles of Psychology," Wm. James, Vol. I. (a most unfavorable critique); "Elements of Physiological Psychology," Ladd; "Human and Animal Psychology," Wundt, Lectures II., III. and IV.; "Outlines of Psychology," Külpe.
  12. "Hermann v. Helmholtz," J. G. McKendrick, p. 284.