Volume 1

A history of the earth, and animated nature / By Oliver Goldsmith. With an introductory view of the animal kingdom, tr. from the French by Baron Cuvier. And copious notes embracing accounts of new discoveries in natural history: And a life of the author by Washington Irving. And a carefully prepared index to the whole work.

  • Oliver Goldsmith
Date:
1847
Catalogue details

Licence: Public Domain Mark

Credit: A history of the earth, and animated nature / By Oliver Goldsmith. With an introductory view of the animal kingdom, tr. from the French by Baron Cuvier. And copious notes embracing accounts of new discoveries in natural history: And a life of the author by Washington Irving. And a carefully prepared index to the whole work. Source: Wellcome Collection.

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    Metaphysics, forms the subject of another science]. But it is the province of the naturalist to ascertain the conditions of the body attendant on sensation,—to trace the extreme gradations of intellect in all living beings,—to investigate the precise point of perfection attainable by each animal,—and, finally, to ascertain whether there be not certain modifications of the intellectual powers, occasioned by the peculiar organization of each species, or by the momentary state of each individual body. It has been already explained, that, to enable the mind to perceive, there must be an uninterrupted communication of nerves between the external organ of sense, and the central masses of the nervous system. The mind is, therefore, conscious only of some impression made upon these central masses. It follows, then, that the mind may be conscious of real sensations, without any corresponding afifection of the external organ; and these may be produced either in the nervous chain of com- munication, or in the central masses themselves. This is the origin of dreams and visions, and of several casual sensations. The various kinds of spectral illusions proceed from impressions, which being made on the retina, are thence communicated to the brain, and are referred by the mind to an object of actual existence. “ Wlien the eye or the head receives a sudden blow, a bright flash of light shoots from the eyeball. In the act of sneezing, gleams of light are emitted from each eye, both during the inhalation of the air, and during its subsequent protrusion; and in blowing air violently through the nostrils, two patches of light appear above the axis of the eye and in front of it, while other two luminous spots unite into one, and appear as it were about the point of the nose, when the eyeballs are directed to it. In a state of indisposition, the phosphorescence of the retina appears in new and more alarming forms. When the stomach is under a temporary derangement, accompanied by headache, the pres- sure of the blood-vessels upon the retina shows itself, in total darkness, by a faint blue light floating before the eye, varying in its shape, and passing away at one side. The blue light increases in intensity—^becomes green and then yellow, and sometimes rises to red; all these colours being fre- quently seen at once; or the mass of light shades off into darkness. When we consider the variety of distinct forms which, in a state of perfect health, the imagination can conjure up when looking into a burning fire, or upon an irregularly shaded surface, it is easy to conceive how the masses of coloured light which float before the eye may be moulded, by the same power, into those fantastic and unnatural shapes which so often haunt the couch of the invalid, even when the mind retains its energy, and is conscious of the illusion under which it labours. In other cases, temporary blind- ness is produced by pressure upon the optic nerve, or upon the retina; and under the excitation of fever or delirium, when the physical cause which produces spectral forms is at its height, there is superadded a powerful influence of the mind, which imparts a new character to the phantasms of the senses.”* Many circumstances render it extremely probable, that the pictures drawn in the mind by memory, or created by imagination, do not merely exist “ in the mind’s eye,” but are actually figured on the retina. During health, and in ordinary cases, these images are faint, and are easily distinguished from the sensations resulting from real perception. It is only when the body is affected by certain diseases, or during sleep, that the impressions on the retina appear to proceed from objects in actual existence. Several instances might be brought forward to illustrate the illusions of the senses. By the well-known experiment of making a galvanic circuit through the tongue, a piece of zinc and one of silver, there is produced a pungent metallic taste, in the same manner as would have followed the real application of a sapid substance. Thus it may be seen that, if we communicate an impression to the nerve on its passage to the central mass, the mind will be affected in the same manner as if the impression had been made on the external organ. By the terms central masses, we understand a certain portion of the nervous system, wliich is always more circumscribed as the animal is more perfectly constructed. In Man it is exclusively a limited portion of the brain. On the contrary, in reptiles the central mass may include either the brain, the entire marrow, or any portion of them taken separately; so that the absence of the entire brain does not deprive them of sensation. The extension of the term, when applied to lower classes of animals, is much greater, as their sensitive power is still more widely diffused. We are hitherto completely ignorant of the nature of tlie changes which take place in the nerves and brain during perception, and of the manner in which the process is carried on. Analogies Letters on Natural Magic, by Sir David Brewster.