Billeder på siden
[ocr errors]

diseases and wounds, nature acting contradictorily and periling the patient's life? 'Why," says Mr. Littré, "does not nature inform us when we swallow a poison? Why does she not reject it? Why does she introduce it into the circulation as if it were useful aliment? Why, finally, when the poison is absorbed, does she bring on convulsions which are of no service to the patient, and which carry him off at last?"

But if there is no power in nature which acts conformably to an object, how are those adaptations produced which astonish us? According to Mr. Büchner it is the energy of the elements and of the forces of matter which, in their fatal and accidental encounter, must have given birth to innumerable forms, which were mutually to limit each other, and answer in appearance to each other, as if made one for another. Among all these forms those alone have survived which have found themselves in some manner adapted to their surrounding conditions. What unhappy attempts must have been undertaken and resulted in abortion, because they have not encountered the conditions necessary to their existence!

It is here that Darwin's book came happily to support Dr. Büchner, by furnishing him the principle he needs to account for the disappearance of certain species and the conservation of others. The system of Darwin rests upon two principles: the principle of natural selection, and the principle of vital competition. All living races dispute for food, all combat against each other for preservation or empire. This state of war that Hobbes dreamed of only among the primitive men, is the universal law of animal life. In this strife the slightest advantages may serve to give the superiority to some over others, to assure the conservation of certain forms and the extinction of those that are less favored. Conformity to an end is then a mere result, and not an intention; it is the result of certain natural causes which accidentally have brought to pass these diverse adaptations.

After having sought to establish that the active force of nature cannot be separated from nature itself, materialists employ the same arguments to present this other force, that we call soul, as a simple function of organization. Let us here follow the reasonings of the school.

If there is a proposition evident to the physiologist and the

physician, it is that the brain is the organ of thought, and that the one is always proportioned to the other. The amount of intelligence is always related to the size, form, and chemical composition of the brain. Let us first speak of the size. The animals which have no brain, or which have only the rudiments thereof, are placed low in the intellectual scale. If some animals seem to have a larger brain than man, it is especially by the development of the parts which preside over the functions of relation and sensation: but those which preside over the functions peculiar to thought are smaller than in man. The form of the brain is not less interesting to study than its size. The causes of the differences in intellect have also been found in the cerebral windings and convolutions. Professor Huschke demonstrated that the intelligence of animal races is proportioned to the number of cerebral sinuosities. According to the celebrated Wagner, who dissected Beethoven's brain, that brain presented deeper and more numerous windings than ordinary brains. The striæ of the brain, hardly visible in the child, augment in the adult, and the intellectual activity augments with them. Observations on insanity and idiocy confirm these data. According to Dr. Porchappe, the weight of the brain diminishes in even ratio with the greater or less intensity of the insanity. Cretinism proceeds always from a malformation of the brain. The majority of doctors are agreed in acknowledgment that in most cases of lunacy morbid alterations are found in the brain, and, if we cannot show them in all cases, it is doubtless owing to the imperfection of our anatomical methods. The same remarks apply to the comparison of the human races. What a difference between the skull of a negro and the noble and developed skull of the European race! If intelligence is in direct proportion to the brain, the converse is not less true. The development and exercise of the understanding develop the brain, as the exercise of the wrestler develops his muscles. If we compare modern skulls with ancient skulls, it is indubitable that the European skulls have considerably enlarged in size. The older the type, the more the skull is developed in the occipital part, the flatter in the frontal part. Hatters know by experience that the cultivated classes need larger hats than the lower classes.

As to the chemical composition of the brain it is much less

simple than might be thought, and it contains complex substances found nowhere else, such as cerebrine, etc. Certain fatty substances seem to have considerable importance in the cerebral composition. The rôle of phosphorus therein is very important, and Moleschott has made bold to say: "Without phosphorus, no thought.'

[ocr errors]

Even while admitting that the soul, thought, is nothing but an organic function, Dr. Büchner combats the celebrated doctrine of Cabanis, that "thought is a secretion of the brain," a doctrine that another materialistic writer thought himself bound to rejuvenate in these words: "There is the same relation between thought and the brain as between the bile and the liver, the urine and the kidneys." Mr. Büchner, indeed, admits that the comparison is not happy, "for," says he justly, "urine and bile are paipable, ponderable, and visible matters; they are furthermore excrementitial matters which the body has used and rejects, while thought is not a substance that the brain produces and rejects, it is the action itself of the brain." The action of a steam-engine must not be confounded with the steam which the engine rejects. Thought is the resultant of all the forces united in the brain; this resultant is not to be seen; it is, according to all appearances, only the effect of nervous electricity. "There is," says Huschke, "the same relation between thought and the electrical vibrations of the nervous filaments of the brain as between color and the vibrations of the ether." It belonged to Moleschott to profoundly sum up this doctrine in these words: "Thought is a movement of matter."

Such are the outlines of the system of Dr. Büchner and the principal arguments of the new German materialism. It is useless to insist upon the last chapters of the book "Matter and Force," chapters which treat of innate ideas, of immortality, of the difference between man and brutes. These chapters are so void of new views, the solutions and ideas are so foreseen by all who are wonted to these questions, that it would be a loss of time for us to pause longer upon them. Such as they are they finish completely the clearest, frankest, and most luminous exposition of the materialistic system that has appeared in Europe since d'Holbach's famous "System of Nature." The author assuredly cannot pretend to any invention, to any orig

inality; but he has collected what was scattered, united what was incoherent, spoken aloud what many secretly think, and that in a short, lively, well-written book. He does us a real service by giving us a real adversary to combat, instead of those intangible phantoms which, floating incessantly between materialism and spiritualism, allow no attack at any point.

[To be continued.]



Heat Considered as a Mode of Motion: Being a Course of Twelve Lectures delivered at the Royal Institution of Great Britain, in the Season of 1862, by JOHN TYNDALL, F. R. S., Professor of Natural Philosophy in the Royal Institution. New York: D. Appleton. PROFESSOR TYNDALL calls this a "New Philosophy." It may be well to inquire in what sense a doctrine held and advocated by leading scientific men for the last century or more is now to be called "new" for there is very little in the philosophy of this book that cannot be found in the writings of eminent physicists from the time of Bacon to the present. Yet these statements of it have been for the most part fragmentary, and in such a form as not to attract the attention of the masses of the lovers of science. It remained for Professor Tyndall to make it popular. With his charming style and brilliant experiments he has embodied the whole philosophy in such a form as to bring it within the comprehension of persons of ordinary intelligence, and to make it not only readable, but as fascinating, to even ordinary readers, as a romance. In a popular sense, therefore, he is really the expounder of a "New Philosophy." He claims no originality, however, for the doctrines he illustrates so strikingly. Yet we think his merit no less than that of the first discoverers of them; for the faculty of stating a doctrine clearly is as rare as that of originating it, and without the one the other would be of but little use to the world. In the advancement of science, therefore, the mission of the expounder is as important as that of the investigator. The popular applause with which these lectures have been received, both in Europe and in this country, we consider to

the fullest extent deserved, for to them the public owes its first acquaintance with this theory of heat, which before had been known only to men of science.

The old corpuscular theory of heat, which this displaces, held that heat was matter--a subtile fluid, which filled the pores of bodies, and, as it were, enveloped their atoms. It was usually defined to be "that substance whose entrance into our bodies causes the sensation of warmth, and its egress the sensation of cold." The capacity of a body for heat meant something likę the capacity of a sponge for water. When a body expanded or became rarer, its capacity was increased, and heat was absorbed and became imperceptible or latent; when compressed again, the heat was forced out and became sensible, as water was squeezed out of a sponge. On this principle the heat produced by friction and percussion was explained. "The dynamical theory, or as it is sometimes called, the mechanical theory of heat, discards the idea of materiality as applied to heat. The supporters of this theory do not believe heat to be matter, but an accident or condition of matter; namely, a motion of its ultimate particles."-Page 39. With regard to the precise character of this molecular motion, no satisfactory theory has been agreed upon. It is yet an open question, to be settled by future investigations. Still, the generally received opinion among physicists seems to have been, that this motion consists in excursions or oscillations of the atom across centers of equilibrium external to itself. Later investigations on this point, however, seem to unsettle this opinion. Professor Tyndall himself, in a paper on Radiant Heat, read before the Royal Society in March last, shows conclusively that "the period of heat-vibrations is not affected by the state of aggregation of the molecules or atoms of the heated body. The force of cohesion binding the atoms together exercises no effect on the rapidity of vibration." Mr. James Croll, in discussing these results of Professor Tyndall's experiments, in the Philosophical Magazine for May, shows that they are hostile to the theory that heat-vibrations consist in excursions of the atoms across centers of equilibrium external to themselves. For, he contends, the relation of an atom to its center of equilibrium depends entirely on the state of aggregation, and, therefore, the period of its excursions across this center of equilib

« ForrigeFortsæt »