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.

    36/660
    the poAver of sensation is concentrated there. Animals of a lower grade have the medullary masses much dispersed; and in the more simple genera, all trace of nerves seems to be lost in the general substance of the body. That part Avhich contains the brain and principal organs of sense is called the head. We now proceed to consider the second animal function—namely voluntary motion. When the animal wills to move, in consequence of a sensation upon an external organ, or any other cause, the motion is transmitted to the muscles by means of the nerves. This power of originating motion, residing in the nervous system of living animals, is one of the most wonderful properties of their nature. Every machine, however complicated or varied in its structure, can only be set in motion by some external power already existing in nature, or produced I by art, whether it be the expansive force of steam, the descent of weights, the action of running water, ; or the recoil of a spring. No perpetual motion can ever be preserved by any arrangement of the parts of a machine among themselves; they must rest ultimately upon a prime mover. But the exquisite arrangement of the animal frame surpasses, in this respect, the highest mechanical skill. The mind wills—the muscle contracts. How much soever we may desire to unravel the mystery, the process is inexplicable, and seems for ever removed beyond the reach of human ingenuity. The only fact hitherto ascertained is, that if the nerve be separated, seriously injured, or even tightly compressed, the motion of the muscle will not follow the volition of the mind. The muscles are bundles of fleshy fibres, by the contraction of which the animal body performs all its motions. The extension and lengthening of the limbs are equally the result of muscular contraction with their bending and drawing in. They are arranged in number and in direction to suit the motions Avhich each animal is destined to perform; and when it becomes necessary to execute these motions with vigour, the muscles are inserted upon hard parts, Avhich are so articulated, one over the other, as to constitute them so many levers. These parts, in the vertebrated animals, are called bones. They are situate internally, and are formed of a gelatin- ous mass [of cellular substance, the pores of which are] penetrated by particles of phosphate of lime. In some of the lower tribes of animals, such as the Mollusca, the Crustacea, and the Insects, these hard parts are external, and composed either of calcareous or of horny substances, called shells, crusts, or scales, all of which are secreted between the skin, and the epidermis or cuticle. A considerable difference is found between the chemical composition of the bones belonging to the higher orders of animals and the external coverings of crustaceous animals. Human bones, when analyzed by Berzelius, were found to contain in 100 parts nearly as follows : of animal mat- ters (being chiefly gelatine, cartilage, and marrow), 34 parts; of phosphate of lime, 51 parts ; of carbonate of lime, 11 parts; of fluate of lime, 2 parts; of phosphate of magnesia, 1 part; and of soda, muriate of soda and water, 1 part. Here the principal ingredient is phosphate of lime; but in j the hard parts of crustaceous animals, such as crabs and lobsters, the carbonate of lime is consider- ably in excess. The shells of the mollusca, such as muscles and oysters, are almost entirely formed of the carbonate of lime. On the contrary, the horny coverings of insects contain a very minute portion of earthy matter, and are mostly composed of animal substances. The same proximate elements enter into the composition of horns, nails, and hoofs, being gelatine, with a membranous substance, resembling the white of eggs boiled hard. The scales of fish are composed of layers of membrane alternately with those of phosphate of lime, which arrangement is the cause of their brilliancy; but the scales of serpents contain no phosphate of lime, and very much resemble, in their constitution, the horny coverings of insects. The fleshy fibres are inserted upon the hard parts, by means of other fibres of a gelatinous nature, called tendons, Avhich seem to be a continuation of the first. These tendons exercise the same office as straps or ropes in ordinary machinery, when it is required to transfer motion from one part to another. By this means a moving power can be exer- cised, in a spot where its immediate presence would be highly inconvenient. Thus, the hand is moved by tendons communicating with muscles, fixed at a considerable distance upon the arm; and the velocity and delicacy of its movements are not obstructed by their presence. Often these tendons are strapped down by cross cords, and pass along grooves in the hones, or through a pulley formed by a ligament. By these mechanical contrivances, the direction in which the muscular power acts may be changed; the forces of different muscles are compounded, and altered in intensity; and the velocity of the resulting motions modified according as circumstances may require. This