Biological agent

“ In the organic world, every individual of necessity springs from some parent, or immediate producing agent; for while inorganic substances are formed by chemical laws alone, we see no case of an animal or plant coming into existence by accident or chance, or chemical operations.
8. Animals and plants are supported by means of nourishment, and die without it. They also increase in size by the addition of new particles of matter to all parts of their substances; while rocks and minerals grow only by additions to their surfaces. ”

“ In plants, from their greater simplicity of structure, organic affections are perhaps entirely limited to the two first forms of animal organic disease; viz. to undue development of tissue in natural situations, and to the formation of natural tissue in parts of a plant where they are not usually found in a state of nature. ”

“ The form of the organism is thus determined by the reaction between external conditions and the inherent activities of the organic molecules of which it is composed; and, as the stoppage of a whirlpool destroys nothing but a form, and leaves the molecules of the water, with all their inherent activities intact, so what we call the death and putrefaction of an animal, or of a plant, is merely the breaking up of the form, or manner of association, of its constituent organic molecules, which are then set free as infusorial animalcules. ”

“ These units in the germ of an organism which cause development into a special structure, cannot be chemical units—cannot be simply molecules of proteid substance in one or other of its forms; since these are not special to any type of creature but common to all creatures. ”

“ So, when we come to consider phylogeny [181] and ontogeny together, we find that if by an organism we mean a thing of contractility or irritability, whose round of movements is kept up by some kind of nutritive process supplied by the environment—absorption, chemical action of atmospheric oxygen, etc.—and whose existence is threatened by dangers of contact and what not, the first thing to do is to secure a regular supply to the nutritive processes, and to avoid these contacts. But the organism can do nothing but move, as a whole or in some of its parts. ”

“ No matter what we may call this point of vital activity in a cell--whether it be a bioplast, a plastid, a physiological unit, or a granule of "elementary life-stuff"--it simply performs the one single function of life to which it is specifically assigned in the process of "building up" any one identical individual of a species, whether it be a man, an ape, a tree, or a parasitic fungus. ”

“ In the first place it is assumed that the fragment of matter out of which each organism arises consists of two portions—one of them, the germ-plasm, reserved within the generative organ of the incipient individual, representing in its components the structure of the species, and gives origin to the germs of future individuals ”

“ Changes in food and feeding may thus accomplish degeneration and induce physiological backsliding of the most typical description. It is a familiar fact that the animal organism is of relatively higher nature than the plant, seeing that the animal frame can, as a rule, feed upon and build up its tissues from organic or living matter only. Animals, in other words, demand the substance of other animals or of plants, or of both combined, as a necessity of their commissariat arrangements. ”

“ All animals therefore, I contend, have a similar cause of their organization, originating from a single living filament, endued indeed with different kinds of irritabilities and sensibilities, or of animal appetencies; which exist in every gland, and in every moving organ of the body, and are as essential to living organization as chemical affinities are to certain combinations of inanimate matter. ”

“ If natural causes have produced a crystal, by successive new combinations of molecules of matter through gradations rising successively into higher forms, why should not natural causes, acting upon other molecules in a corresponding way, have produced organic life, or animated organisms? If natural causes have evolved out of certain molecules the substance known as organizable protein, why should not the continued operation of the same or similar causes have modified organizable protein into some distinct and recognizable animated organism? ”

“ Out of the blood all of the tissues are wrought, each in its kind, and every tissue is a kind of its own, and there are kinds of kinds, so that the animal organism is a chemical laboratory engaged during the existence of the animal in building up more complex substances and tearing them down into more specialized substances, and this is metabolism, or zoochemistry. ”

“ If the famous suggestion, that all animal and vegetable life results from a single vital germ, and that all the different animals and plants now existent were developed by a natural process of evolution from that germ, were a demonstrated truth, we should still be able to point to the evidence of intelligence displayed in the measured and progressive development, in those exquisite forms so different from what blind chance could produce, and in the manifest adaptation of surrounding circumstances to the living creature, and of the living creature to surrounding circumstances. ”

“ There is a great struggle for existence between the various species, and the circumstances determining the survival of this or that organism are extremely complicated, and we are yet very much in the dark as to the action of the various chemical compounds contained in the puer, so that it is unsafe to neglect even those which are present in only small amounts. Very minute quantities of certain bodies, almost too small for detection by chemical means, are sufficient to cause large differences in the growth of certain organisms. ”

“ Man and the neighbouring species, which are the particular object of our researches, enjoy then evidently, all the vital properties, some of which belong to organic life, the others to animal life. 1st. Organic sensibility and insensible contractility have all the phenomena of the capillary circulation, of secretion, of absorption, exhalation, nutrition, &c. evidently dependant upon them in a state of health. In treating, therefore, of these functions, we must always ascend to these properties. ”

“ Both animals and plants take their water and inorganic salts directly as such. The animal cell can absorb its carbohydrate and proteid food only in the form of carbohydrate and proteid; it is dependent, in fact, on the pre-existence of these organic substances, themselves the products of living matter, and in this respect the animal is essentially a parasite on existing animal and plant life. ”

“ The higher we climb in the scale of organization, particularly in the animal kingdom, the more do we meet with cells which are entrusted with special functions. For instance, we find cells which receive matter from the exterior. Others transform particular compounds into products of a special nature. Others, again, have the function of carrying the final products of metabolism to definite points for excretion.
A unicellular organism stands constantly in relation with numerous substances of the outer world, which differ from place to place and from time to time.. ”

“ But the everlasting wonder is, how all the characteristics of a species can be embodied in a germ so as to be reproduced by growth; and still more amazing is it how the nicer shades of organic modification are also transmitted by the germ so as to become hereditary. In some way the systems of organic molecules must be capable of taking and retaining an infinite number of inconceivably delicate impressions; for with the myriad forms of life there must be formed myriads of molecular modifications of germ structure. ”

“ IT has occurred to the writer that the adoption of the germ theory of disease necessarily involves the application of the theory of evolution, and that here may be found a means of accounting for the genesis of the various forms of disease. Germs are living matter; they must therefore be under the influence of those laws and forces which condition all living matter. ”

“ In fact, many of the organisms are identical with those which cause putrefaction. It will be seen, therefore, that no single species produces the complex chemical and physiological changes which take place, or the bodies necessary for the bating of skin, as some observers have supposed; but the various species succeed one another as the medium changes its reaction and composition, until finally the organic portion is resolved into the simplest bodies such as carbon dioxide, ammonia, and hydrogen. ”

“ Thus Part I. deals with organic matter and its activity or metabolism, the action and reaction between organisms and their environment, the correspondence between organisms and their circumstances, and similar general data. Part II. states the big inductions regarding growth, development, adaptation, heredity, variation, and so on. Part III. deals with the arguments suggestive of organic evolution and with the factors in the process. Part IV. is a detailed interpretation of the evolution of organic structure, and Part V. an analogous interpretation of the evolution of functions. ”

“ Thus we should expect the latent "life" of the germ, egg, or seed, to be less easily extinguished than the more subtile, and, at the same time, more active life of the fully-developed tissue-element or organism ”

“ Such simple cells can exhibit in very low form all the activities the higher animals show in much more elaborate development. A one-celled animal can move about, can recognize the proximity of food, can engulf its food and digest it, can build up its own substance out of the digested food, can absorb oxygen, [Pg 165] can use this oxygen in the burning of its own substance to produce its own activities, can act in response to sensation gained from outside, can throw off its waste matter produced by its own activities, and can grow. ”

“ We come next to the agency of chief importance among those that work changes in organic matter; namely, chemical affinity. How readily vegetal and animal substances are modified by other substances put in contact with them, we see daily illustrated. Besides the many compounds which cause the death of an organism into which they are put, we have the much greater number of compounds which work those milder effects termed medicinal—effects implying, like the others, molecular re-arrangements. ”

“ These slightly-different units severally multiply at the expense of the nutriment supplied to the unfolding germ—each kind moulding this nutriment into units of its own type. Throughout the process of development the two kinds of units, mainly agreeing in their proclivities and in the form which they tend to build themselves into, but having minor differences, work in unison to produce an organism of the species from which they were derived, but work in antagonism to produce copies of their respective parent-organisms. ”

“ The fact that it is possible to propagate these cells of one animal for years in other animals of the same species, without any loss of their vegetative vitality, suggests that this continued growth is kept up by a growth-stimulating substance present in the proper species of animal ”

“ It is clear that the organism that best uses its organs has, other things equal, the best chance of survival. It will therefore hand on to its offspring germinal matter with an inherent tendency to make vigorous use of its faculties.
Those who argue thus deny that the body-cells can in any way affect the germ-cells. To account for any continuous increase in faculty, they invoke variation and the selection of favourable varieties. What, then, we may now ask, is, on their view, the mode of origin of variations? ”

“ We turn now, however, to the consideration of a matter of even more fundamental importance; for when we come to study bacteria in Nature, we find that there are certain natural processes connected with the life of animals and plants that are fundamentally based upon their powers. Living Nature appears limitless, for life processes have been going on in the world through countless centuries with seemingly unimpaired vigour. At the very bottom we find this never-ending exhibition of vital power dependent upon certain activities of micro-organisms. ”

“ Among these is sexual selection, and, taking a broad view, we may also include selection by man. In order, then, to the attainment of greater exactness, may we not give a name to that form of natural selection which has been potent in bringing about the variations in the characteristics of those germs to which the differences in the forms of disease are due? Such a term may be found, I would suggest, in "tissue-selection," as indicating the special means whereby the constitution of the germs has been modified. ”

“ Some of the unicellular forms of life, and some organisms consisting of a few groups of cells, are, at least in part, equipped with agents (ferments) which are not so precisely directed against certain substrates as the ferments of the higher species, such as plants and animals. ”

“ Q. What is the peculiarity of living matter as to the power of nutrition and growth? A. The non-living increases in size by external additions; but bioplasm selects appropriate material from its food, or pabulum, changes the chemical relations of this material, and appropriates it to its own structure in such a way that it grows from within.
14. Q. What is the peculiarity of bioplasm as to reproduction A. Bioplasm can generate or reproduce its own kind of living matter.
15. Q. What power has a living thing to preserve its own identity? ”