Animal chemistry, or, Organic chemistry in its applications to physiology and pathology / by Justus Liebig ; edited from the author's manuscript by William Gregory.

  • Liebig, Justus, Freiherr von, 1803-1873.
Date:
1845
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Licence: Public Domain Mark

Credit: Animal chemistry, or, Organic chemistry in its applications to physiology and pathology / by Justus Liebig ; edited from the author's manuscript by William Gregory. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    ORGANIC CHEMISTRY APPLIED TO PHYSIOLOGY AND PATHOLOGY. I. In the animal ovum, as well as in the seed of a plant, we recognise a certain re- markable force, the source of growth, or in- crease in the mass, and of reproduction, or of supply of the matter consumed; a force in a state of rest. By the action of external influences, by impregnation, hy the pre- sence of air and moisture, the condition of static equilibrium of this force is disturbed ; entering into a state of motion or activity, it exhibits itself in the production of a series of forms, which, although occasionally bounded by right lines, are yet widely dis- tinct from geometrical forms, such as we ob- serve in crystallised minerals. This force is called the vital force, or viz vitce vitality. The increase of mass in a plant is deter- mined by the occurrence of a decomposition which takes place in certain parts of the plant under the influence of light and heat. In the vital process, as it goes on in vegetables, it is exclusively inorganic matter which undergoes this decomposition; and if, with the most distinguished mineralo- gists, we consider atmospherical air and certain other gases as minerals, it may be said that the vital process in vegetables ac- complishes the transformation of mineral substances into an organism endued with life; that the mineral becomes part of an organ possessing vital force. The increase of mass in a living plant implies that certain component parts of its nourishment become component parts of the plant; and a comparison of the chemical composition of the plant with that of its nourishment, makes known to us, with positive certainty, which of the component parts of the latter have been assimilated, and which have been rejected. The observations of vegetable physiolo- gists and the researches of chemists have mutually contributed to establish the fact, that the growth and development of vege- tables depend on the elimination of oxygen, which is separated from the other compo- nent parts of their nourishment. In contradiction to vegetable life, the life of animals exhibits itself in the continual absorption of the oxygen of the air, and its combination with certain component parts of the anima* body. While no part of an organized being can serve as food to vegetables, until, by the processes of putrefaction and decay, it has assumed the form of inorganic matter, the animal organism requires, for its support and development, highly organized atoms. The food of all animals, in all circum- stances, consists of parts of organisms. Animals are distinguished from vegeta- bles by the faculty of locomotion, and, in general, by the possession of senses. The existence and activity of these dis- tinguishing faculties depend on certain in- struments which are never found in vegeta- bles. Comparative anatomy shows, that the phenomena of motion and sensation de- pend on certain kinds of apparatus, which have no other relation to each other than this, that they meet in a common centre. The substance of the spinal marrow, the nerves, and the brain, is in its composition, and in its chemical characters, essentially distinct from that of which cellular sub- stance, membranes, muscles, and skin are composed. Every thing in the animal organism, to which the name of motion can be applied, proceeds from the nervous apparatus. The phenomena of motion in vegetables, the circulation of the sap, for example, observed in many of the characese, and the closing of flowers and leaves, depend on physical and mechanical causes. A plant is destitute of nerves. Heat and light are the remote causes of motion in vegetables; but in ani- mals we recognise in the nervous apparatus a source of power, capable of renewing itself at every moment of their existence. While the assimilation of food in vegeta- bles, and the whole process of their forma- tion, are dependant on certain external in- fluences which produce motion, the deve- lopment of the animal organism is, to a certain extent, independent of these external influences, just because the animal body can produce within itself that source of mo- tion which is indispensable to the vital pro- cess. Assimilation, or the process of formation and growth—in other words, the passage of matter from a state of motion to that of rest '—goes on in the same way in animals and