Biology: Life and Organisation. Classification of the Phenomena of Life.
It may be safely said of all those living things which are large enough to enable us to trust the evidence of microscopes, that they are heterogeneous optically, and that their different parts, and especially the surface layer, as contrasted with the interior, differ physically and chemically; while in most living things, mere heterogeneity is exchanged for a definite structure, whereby the body is distinguished into visibly different parts which posses different powers or functions. Living things which present this visible structure are said to be organized; and so widely does organization obtain among living beings, that organized and living are not unfrequently used as if they were terms of co-extensive applicability. This, however, is not exactly accurate, if it be thereby implied that all living things have a visible organization, as there are numerous forms of living matter of which it cannot properly be said that they possess either a definite structure or permanently specialized organs: though, doubtless, the simplest particle of living matter must possess a highly complex molecular structure, which is far beyond, the reach of vision.
The broad distinctions which, as a matter of fact, exist between every known form of living substance and every other component of the material world, justify the separation of the biological sciences from all others. But it must not be supposed that the differences between living and not-living matter are such as to justify the assumption that the forces at work in the one are different from those which are to be met with in the other. Considered apart from the phenomena of consciousness, the phenomena of life are all dependent upon the working of the same physical, and chemical forces as those which are active in the rest of the world. It may be convenient to use the terms "electricity" and "electrical force" to denote others; but it ceases to be proper to do so, if such a name implies the absurd assumption that "electricity" and "vitality" are entities playing the part of efficient causes of electrical or vital phenomena. A mass of living protoplasm is simply a molecular machine of great complexity, the total results of the working of which, or its vital phenomena, depend, -- on the one hand upon its construction, and, on the other, upon the energy supplied to it; and to speak of "vitality" as anything but the name of a series of operations is as if one should talk of the "horologity" of a clock.
Living matter, or protoplasm and the products of its metamorphosis, may be regarded under four aspects:
(1.) It has a certain external and internal form, the latter being more usually called structure;
(2.) It occupies a certain position in space and in time;
(3.) It is the subject of the operation of certain forces in virtue of which it undergoes internal changes, modifies external objects, and is modified by them; and
(4.) Its form, place and powers are the effects of certain causes.
In correspondence with these four aspects of its subject, biology is divisible into four chief subdivision – I. MORPHOLOGY; II DISTRIBUTION; III. PHYSIOLOGY; IV. AETIOLOGY.
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Biology - Table of Contents