Disease in plants / by H. Marshall Ward.

  • Harry Marshall Ward
Date:
1901
Catalogue details

Licence: In copyright

Credit: Disease in plants / by H. Marshall Ward. Source: Wellcome Collection.

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    energy concerned is primarily what is usually termed chemical energy, and that every compound entering into the protoplasm carries in a supply of this, available in various ways. Death, on the contrary, is the cessation of these rhythmical processes of building up and breaking down of the protoplasm molecules. It does not imply the cessation of chemical changes of other kinds, but that these rhythmical con- structions of the complex and labile protoplasm molecules breaking down on stimulation to bodies partly re-assimilable, partly combustible in respira- tion, and partly excretory, etc., have ceased, and that further chemical changes in the material are thenceforth simpler and different in kind and degree, eventually leading to total disintegration so that no units are left capable of restoring the rhythm. If these ideas are correct, we may define Disease as dangerous disturbances in the regularity, or interference with the completeness or range of the molecular activities constituting normal Life— i.e. Health—and it is evident that every degree of transition may be realised between the two extremes. Now, if we further assume, as I think we must do, that a considerable range or “ play ” must exist in the molecular activities of the protoplasm constituting life, we obtain a sort of expression of what we mean by limits of variation. The fact that life can go on in a given plant at temperatures between from i°-5° and 35°-40° C., or in lights of different intensity, or within
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