Handbook of physiology / by W. D. Halliburton.

  • Halliburton, W. D. (William Dobinson), 1860-1931.
Date:
1900
Catalogue details

Licence: In copyright

Credit: Handbook of physiology / by W. D. Halliburton. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    with mucin, and in adipose tissue, where they become charged with fat. The term cell was first used by botanists ; in the popular sense of the word a cell is a space surrounded by a wall, as the cell of a prison, or the cell of a honey-comb, In the vegetable cell there is a wall made of the starch-like material called cellulose, within this is the living matter, and a number of large spaces or vacuoles filled with a watery fluid. The use of the term cell by botanists was therefore completely justified. But the animal cell is different; as a rule, it has no cell-wall, and no vacuoles. It is just a little naked lump of living material. This living material is jelly-like in consistency, possessing the power of movement, and the name protoplasm has been be- stowed on it. Somewhere in the protoplasm of all cells, generally near the middle in animal cells, is a roundish structure of more solid consistency than the rest of the proto- plasm, called the nucleus. An animal cell may therefore be defined as a mass of protoplasm containing a nucleus. The simplest animals, like the amoebae, consist of one cell only: Fig. 2.—Animal cell consisting of protoplasm containing a nucleus. Fig. 3.—Amoebae unicellular animals. Fig. 4.—Cells of tbe yeast plant in pro- cess of budding; unicellular plants. the simplest plants, like bacteria, torulse, etc., consist of one cell only. Such organisms are called unicellular. In the progress of their life history the cell divides into two; and the two new cells separate and become independent organisms, to repeat the process later on.