A manual of physiology : with practical exercises / by G.N. Stewart.

Date:
1900
Catalogue details

Licence: In copyright

Credit: A manual of physiology : with practical exercises / by G.N. Stewart. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    CHAPTER I. THE CIRCULATING LIQUIDS OF THE BODY. In the living cells of the animal body chemical changes are constantly going on; energy, on the whole, is running down; complex substances are being broken up into simpler combinations. So long as life lasts, food must be brought to the tissues, and waste products carried away from them. In lowly forms like the amoeba, these functions are per- formed by interchange at the surface of the animal without any special mechanism ; but ip all complex organisms they are the business of special liquids, which circulate in finely branching channels, and are brought into close relation at various parts of their course with absorbing organs, with eliminating organs, and with the tissue elements in general. In the higher animals, three circulating liquids have been distinguished: blood, lymph, and chyle. But it is to be remarked that chyle is only lymph derived from the walls of the alimentary canal, and therefore, during digestion, containing certain freshly - absorbed constituents of the food ; while both ordinary lymph and chyle ultimately find their way into the blood, and are in their turn recruited from it. The blood contains at one time or another every- thing which is about to, become part of the tissues, and everything which has ceased to belong to them. It is at once the scavenger and the food-provider of the cell. But no bloodvessel enters any cell; and if we could unravel the complex mass of tissue elements which essentially constitute what we call an organ, we should see a sheet of cells, with capillaries in very close relation to them, but everywhere