Elements of human physiology / by Henry Power.

  • Henry Power
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by Henry Power. Source: Wellcome Collection.

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    ammonia, from which they were originally built up. The results are similar in both cases ; the essential difference is that in life the conditions are adapted for the renewal of the complex molecules with all their activities by the supply of new material and the re- moval of the old and effete substances ; whilst in death no renovation is possible, and the play of chemical affinities gradually reduces the several compounds to the simplest combinations of their elements. In the lower forms of life the structure is simple, and as there is no distinction of organs every part is capable of discharging a number of functions, each of which in the higher animal is limited to a special organ. The simplest forms of living beings with which we are acquainted are found in the class to which the term Protista is applied. In these the body is com- posed of a mass of protoplasm, through which granules are usually scattered, and the whole, or any part of it, can absorb nutriment from without, digest it, apply it to the nutrition of its own structure, cast out the indigestible matter, move from place to place, respond by movement to stimulation of various kinds, and undergo multiplication by division. In the higher animals each of these functions is limited to a definite organ. An alimentary canal is destined to digest the food, and prepare it for absorption into the circulating fluids. Definite vessels are formed, one segment being develojDed into a pulsating organ or heart, by which the fluids elaborated into blood are driven to all parts of the system, whilst special organs, as the bones, cartilages, muscles, and nerves, are subservient to movement, and to the reception, conduction, and the perception of impulses from without, and there are yet others which are subservient to reproduction. Oeneral composition of tlie body.—The body is composed of certain ultimate elements united in part to form inorganic compounds, and in part
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