Text-book of human physiology : including histology and microscopical anatomy with especial reference to the practice of medicine / by L. Landois.

  • Landois, L. (Leonard), 1837-1902.
Date:
[1904], ©1904
Catalogue details

Licence: Public Domain Mark

Credit: Text-book of human physiology : including histology and microscopical anatomy with especial reference to the practice of medicine / by L. Landois. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    accordingly, is the smallest portion of a Ijody that is capable of existence in a free state, and that, further, as a unit no longer exhibits the aggre- gate condition. The molecule is, however, not the ultimate unit of the body. On the contrary, every molecule consists of a collection of the smallest units, which are known as atoms. An atom is incapable of occurring alone in a free state, but atoms unite with other atoms of the same or of different character to form atom-complexes, desig- nated molecules. Atoms are unconditionally insusceptible of division; whence the name. Atoms, further, are conceived to be of constant size and solid in themselves. From the chemical standpoint the atom of an elementary body (element) is the smallest amount of an element that is capable of entering into chemical combination. Just as ponderable matter consists in its ultimate parts of ponderable atoms, so also does the ether, imponderable matter, consist of analogous particles of smallest size, namely, ether-atoms. Within ponderable matter the ponderable atoms are arranged in quite a definite order with relation to the ether-atoms. The ponderable atoms are drawn mutually toward one another (attraction); the pon- derable atoms likewise attract the imponderable atoms; but the ether- atoms mutually repel one another. It thus comes about that in the ponderable mass ether-atoms are collected about every ponderable atom. These collections, designated dynamids by Redtenbacher, tend, in accordance with the powers of attraction of the ponderable atoms, to approach one another, but only so far as permitted thus to do by the repellent power of the surrounding ether-atoms. Therefore the pon- derable atoms can never cohere without interstices, but the entire mass of matter must be considered as loose in texture in consequence of the interposed ether-atoms, which prevent immediate contact between pon- derable atoms. The aggregate condition of the body depends therefore upon the mutual arrangement of the molecules (namely, those sinall particles of matter that may still occur isolated in a free state). Within solid bodies, which are characterized by constancy of volume, as well as independence of form, the molecules are arranged in a fixed and unchangeable relation with one another. In fluid bodies, which are characterized by constancy of volume, though by variability of form, the molecules are in constant movement, just as in a mass of moving worms or insects the individual animals are incessantly changing their place with relation to one another. If this movement of the molecules attains such proportions that the individual molecules scatter in all directions (just as the moving collection of insects separates into its constituent parts), the body becomes gaseous, and is characterized in this form both by its inconstancy of form and its variability in volume. The study of molecules and their motor phenomena is the part of physics. FORCES. Gravitation; Work of a Force.—All phenomena appertain to matter. They are the appreciable expression of the forces inherent in matter. The forces themselves are not appreciable; they are the causes of the phenomena. The first of the forces to be considered is gravita- tion. According to the law of gravitation every particle of ponderable matter in the universe attracts every other particle with a certain degree