Catabolism

“ The concentration of the solution is increased, the osmotic pressure is raised, and we have a hypertonic centre of diffusion. Every centre of catabolism is therefore a positive pole of diffusion. Similar considerations as to the formation and breaking up of the molecules in anabolism and catabolism apply to polymerization. ”

“ It may be impracticable to outline in terms of metabolism the precise processes of waste and repair in organs and organisms, or to define the relative periods of action and assimilation (or of catabolism and anabolism) best adapted to the development of motile tissue ”

“ As is well known, the nutrition of man is supplied by the organic substances, protein, carbohydrates, and fat; these are found in various combinations in animal and vegetarian foods, and as a rule contain also much of the inorganic or mineral substances necessary for the system; all of 111these with water, and its salts, and oxygen, supplied by the lungs, unite, through anabolism and catabolism, to build and maintain the human body in health. ”

“ The metabolism, however, proceeds, the disintegration of living substance continues, although at a slower rate, but produces an accumulation of other products. Whereas formerly during the existence of a sufficient supply of oxygen an oxydative disintegration of nitrogen-free groups into carbon dioxide and water took place, both of which could easily be eliminated from the cell, the anaërobic disintegration furnishes only complex products, having a higher carbon content, such as lactic acid, fatty acids, aceton,84 etc. These, being more difficult to excrete from the cell, accumulate. ”

“ That is, through a shifting or rearrangement of the atoms in the compounds used as food the oxidation of carbon is brought about. Enzymes are probably responsible for this action. Carbon dioxide is produced by anaërobes as well as by aërobes, and frequently in amounts readily collected. A carbohydrate is usually though not always essential for the growth of anaërobes and serves them as the best source of energy.
Nitrogen is the characteristic element of living material. Protoplasm is a chemical substance in unstable equilibrium and nitrogen is responsible for this instability. ”

“ The animal body may for our present purpose be regarded as consisting, besides water, of proteine and non-nitrogenous matter, chiefly fat: the latter contains the elements carbon, hydrogen, and oxygen; the former, in addition to these three, nitrogen. Both classes of matter are gradually oxidized in the body, and are finally converted into carbonic acid, water, and urea, the former of which is excreted through the lungs and skin, the latter through the kidneys, and the water partly by all three channels. ”

“ We must recognize the enzyma as catalysators that arise in the organism during the life of the cells, and by their action relieve the living being of the greater part of its duties. Not only are digestion and assimilation controlled by enzyma from first to last, but the fundamental vital action of most organisms, the production of the necessary chemical energy by combustion at the expense of the oxygen in the air, takes place with the explicit co-operation of enzyma, and would be impossible without them. ”

“ There is not the slightest doubt that the course of this metabolism, as well as the inter-relations of the cells of a particular organ, is only imaginable under the supposition that the metabolism of the whole organism is regulated in the most precise way, not only quantitatively, but also qualitatively. We are bound to imagine that, in the work of the cells, the same stages of decomposition recur regularly, and that it is at a quite definite stage that the by-products of metabolism are passed by the cells into the lymph channels, and so into the blood system. ”

“ With the aid of these enzymes, the albuminoid substances are 'peptonized.' In the laboratory such organisms are described as gelatin-liquefying bacteria. A part of the food thus made accessible is appropriated by the microorganisms and in their physiological processes is still further simplified. A part of the carbon is oxidized and escapes into the atmosphere as carbon dioxide, gaseous hydrogen or oxygen is set free, or the two are combined to form water. The nitrogen with which we are here concerned is subject to many changes. ”

“ Plants in the process of digestion break up carbonic acid into the two elements of which it is composed, namely, carbon and oxygen, keeping the carbon and setting free the oxygen. As carbonic acid occurs always in the air in small quantities, the result of this is that plants remove carbonic acid from the atmosphere, and give out oxygen.
3. Animals, on the other hand, have no power of living on inorganic matters, such as water, carbonic acid, and ammonia. They have no power of converting these into the complex organic substances of which their bodies are composed. ”

“ Our conception of the processes involved in proteid katabolism is that of a series of progressive chemical decompositions, in which intracellular enzymes play the all-important part. The intermediary products formed are definite bodies because of the specific nature of the active enzymes, and, secondly, because of the chemical nature of the substances acted upon. In other words, oxidation in the animal body takes the shape of a series of well-defined chemical reactions, in which chemical constitution and specific enzyme action are the predetermining cause. ”

“ Cultivated in broth it gives off much gas, consisting of 12 per cent. carbon dioxide, 85 per cent. hydrogen, 3 per cent. oxygen. If glucose be added, the quantity of carbon dioxide rises to 40 per cent., and acid is produced. The most rapid growth is at 37° C., and at this temperature a broth culture has a distinct reducing action on skin. According to the medium in which it is grown, it produces acid or alkali, and thus comes under the heading of mixed bacteria. In sugar81 solutions acid is produced, and in proteid solutions ammonia compounds, indol, and evil-smelling gases are given off. ”

“ But all our experience, hitherto, has proved, that even those cells which are constructed on a simple plan morphologically do, when studied from a purely chemical point of view, show exceedingly complicated relations. Indeed, the study of the processes of metabolism in unicellular forms of life is a study all the more difficult, in comparison with that of more complicated organisms, in that, in the former, it is so difficult to separate the actually absorbed materials from the metabolic by-products, and these again from the secretory or excretory products. ”

“ Bacteria require for their growth, nitrogen, hydrogen, carbon, oxygen, together with a limited amount of mineral matter. The nitrogen and carbon are most available in the form of organic compounds, such as albuminous material. Carbon in the form of carbohydrates, as sugar or starch, is most readily attacked by bacteria. ”

“ What proportion of the ever varying output of this gaseous product of metabolism comes from the oxidation of organized tissue material, and what from the oxidation of circulating carbohydrate and fat and unorganized material in general? We have learned, for example, that the excretion of carbonic acid runs more or less closely parallel with the degree of muscular activity, and we should possess the means of discriminating between the output from true tissue oxidation and that which is derived from extra-cellular sources. ”

“ When I stated that carbonic acid was formed in the venous blood in the processes of life, I meant merely to say that this blood, in consequence of certain changes, became capable of giving off carbon and oxygen in union with each other, for the moment inorganic matter enters into the composition of living organs it obeys new laws. The action of the gastric juice is chemical, and it will only dissolve dead matters, and it dissolves them when they are in tubes of metal as well as in the stomach, but it has no action upon living matter. ”

“ The conception of ascending steps of constructive metabolism resulting in the formation of protoplasm and the storing of energy, with correlated descending steps, by which protoplasm is transformed into less complex compounds (destructive metabolism) , with a liberation of energy, serves as a key to the complex processes of nutrition which enables us to trace their conformity to general laws that are readily recognized, and clears up the obscurity arising from the multiplicity of details which from other points of view could not be brought into consistent relations. ”

“ These minute tubes are lined with capillary blood-vessels, which are constantly sending out not only carbonic acid, but other gases and particles of decayed matter. The skin and lungs together, in one day and night, throw out three quarters of a pound of charcoal as carbonic acid, beside other gases and water.
While the bodies of men and animals are filling the air with the poisonous carbonic acid, and using up the life-giving oxygen, the trees and plants are performing an exactly contrary process; for they are absorbing carbonic acid and giving out oxygen. ”

“ Protoplasm, be it in plant or animal, breathes and throws off waste materials. When a living thing does work oxygen unites with food in the body; the food is burned or oxidized and work is done by means of the energy released from the food. The waste materials are excreted or passed out. Plants and animals alike pass off the carbon dioxide which results from the oxidation of food and of parts of their own bodies. Animals eliminate wastes containing nitrogen through the skin and the kidneys. ”

“ In katabolism, this accumulated material, and in some degree the living substance itself, is broken down or disintegrated with liberation of the stored-up energy, which manifests itself in the form of heat and mechanical work. At times, the anabolic processes predominate and there is a relatively large accumulation of stored-up materials; while at other times, katabolism, with its attendant chemical decompositions, predominates, and the body loses correspondingly. The point to be emphasized here is that the living body, with its multitude of living cells, is the seat of incessant change. ”

“ Of these, carbon and oxygen unite, in certain proportions and under certain conditions, to give rise to carbonic acid; hydrogen and oxygen produce water; nitrogen and hydrogen give rise to ammonia. These new compounds, like the elementary bodies of which they are composed, are lifeless. But when they are brought together under certain conditions they give rise to the still more complex body, protoplasm, and this protoplasm exhibits the phenomena of life.’
Until we have further knowledge of the changes which constitute these phenomena, physiology must remain descriptive rather than explanatory. ”

“ The cell, as has already been mentioned, always works by degrees, for it is quite incapable of suddenly decomposing a complicated molecule, and of directly transforming it by means of combustion into its final products. The cell builds step by step, and so preserves the equilibrium of its energic metabolism. The rapid combustion of albumen, fats, and polysaccharides would, in certain places, suddenly produce a great deal of energy, which would appear in the form of heat, and under certain circumstances would destroy the life of the cell itself. ”

“ On the one hand we shall have to decide whether defensive ferments exist that are directed against specific micro-organisms, and, further, whether the tissue attacked is decomposed by blood serum. Either the micro-organisms will be able to decompose the tissue—their nutritive medium—in a manner harmonious with themselves and disharmonious with the body, and so produce decomposites out of harmony with the plasma, or else the injured tissue will be altered in such a way as to be no longer able to continue the normal processes of its metabolism. ”

“ Outside the animal body, the customary components of our daily food, the proteins, fats and carbohydrates, are not affected by oxygen even at the body temperature or by long exposure to the gas. Catalytic action is a necessary prelude to their oxidation, and it is the smaller molecules resulting from the action of enzymes working through catalysis that are mainly burned up or broken down with liberation of their contained energy. ”

“ It cannot be claimed that the complex chain of transformations which organic chemistry has demonstrated in the destructive metamorphosis of albumen and starch in the laboratory is represented in the vital chemistry of the body. All that can be said in the present state of knowledge is, that the metabolism of food is in its nature a chemical analysis, modified and regulated by vital force, and resulting in the building up of tissues and in the conversion of potential into active energy. ”

“ As to the metabolism within the cell, no more is known than is the case with other cells, nor even as much. The materials used for growth and as sources of energy are taken into the cell, built up into various compounds some of which have been enumerated and in part broken down again. Carbon dioxide and water are formed in the latter process. ”

“ Carbon is necessary not only because it is an essential constituent of protoplasm but because its oxidation is the chief source of the energy necessary for the internal life of the cell, though nitrogen and sulphur replace it in this function with a few forms. This latter use of carbon constitutes what may be called its respiratory function. Bacteria like other organisms in their respiration utilize oxygen and give off carbon dioxide. ”

“ Many Bacteria exhibit processes of metabolism totally different from those generally laid down in textbooks as characteristic of living matter; some are killed by free oxygen; others can absorb free nitrogen, and various other “abnormal” properties are manifested by them. ”