Physiological chemistry

“ It needs no imagination to foresee what a full knowledge of the chemical constitution of all types of proteid matter will mean for the physiologist and physiological chemist. Much that is now cloudy and uncertain in our understanding of cell and tissue metabolism, in our comprehension of nutritive changes in general, of digestive proteolysis and of intracellular autolysis, will become clear as crystal. ”

“ It was in this fifteenth century that the sect of chemical physicians arose, who claimed that all the phenomena of the living body could be explained by the same chemical laws as those that rule inorganic matters. Although the illustrations and proofs which they adduced were completely unsatisfactory, yet the tendency at the present time is in the same direction, since chemistry and physiology are better known. ”

“ When the animal dies decay supervenes as a chemical process. The metabolic organs, therefore, are the organs of digestion which prepare the food for the blood, the organs of secretion which furnish material to aid digestion, and the organs of excretion. The science of the chemistry of animate substances is yet in its infancy and the kinds appearing in the animate realm are at the present stage of research vicariously represented by forms. ”

“ Oxygen, also, comports itself differently in the tissue; as is proved by the fact that its physiological absorption is markedly different from any chemical oxidation in a dead or decomposing tissue.20 Be this as it may, we know that organic substances have to be unbuilt and rebuilt in the organism; that the albumen of our food never passes directly53 into the albumen of our tissues; any more than the milk drunk by a nursing mother will pass into her breasts, and increase her supply, except by nourishing her. ”

“ Life, to all appearance, is but the result of combined chemical and mechanical processes. Assimilation, digestion, secretion, are explainable by chemistry, and by chemistry alone. The stomach is a chemical retort, the body a chemical laboratory. Carbon, oxygen, hydrogen, nitrogen, combine and separate in the body as out of the body. The blood circulates upon purely mechanical principles; all muscular action is mechanical. In the phenomena of life, the only perceptible difference is in the combinations of fundamental elements; yet chemistry and mechanics cannot produce a live body. ”

“ Such results are of great interest, for they show that cells which, as regards their main physiological office, the conveyance of oxygen to the tissues, seem to be governed strictly by the physical laws of diffusion of gases, appear to exercise a kind of 'selection' in the taking up of many substances which have nothing to do with their particular function. ”

“ In many other cases the physiological effect of the compound was distinctly foreseen, and latterly the relation between chemical constitution and physiological action has become the objective of much research. It may be reasonably anticipated that before many years have passed it will be possible to predict the physiological powers of a substance from a knowledge of its structural formula, just as already many of its more noteworthy physical properties may be so foretold. ”

“ If the demand for a substance is absolute its chance to act and answer that call and obey such command must not be hindered while in preparation, nor on its journey to local destination, for by its power all action may depend. Thus blood, albumen, gall, acids, alkalies, oils, brain fluid and other substances formed by associations while in physiological processes of formation must be on time in place and measured abundantly, that the biogenic laws of nature can have full power with [Pg 150] time to act, and material in abundance and of kinds to suit. ”

“ Further, recognizing as we must the extreme sensitiveness of the central and peripheral parts of the nervous system to changes in the composition of the blood, we see suggested indirect ways by which metabolism, both general and local, may be modified by influences exerted upon the nervous system, whereby the nutritive condition of individual structures may undergo change. ”

“ Swallowing our food is a mechanical process, the digestion of it is a chemical process and the assimilation and elimination of it a vital process. Inhaling and exhaling the air is a [Pg 214] mechanical process, the oxidation of the blood is a chemical process, and the renewal of the corpuscles is a vital process. Growth, assimilation, elimination, reproduction, metabolism, and secretion, are all vital processes which cannot be described in terms of physics and chemistry. ”

“ The justification to speak of an equilibrium of metabolism arises from investigations of metabolism in mammals. The classical experiments of the previous century, as is well known, have shown that in the adult mammal receiving a necessary quantity of nourishment and in a state of rest, the intake and outgo of the constituent elements are the same. The carbon, hydrogen, nitrogen, oxygen, sulphur, phosphorus, etc., taken in during a lengthened period in the form of food and respired air, appear again in equal quantity, in other combinations, in the products of excretion of the organisms. ”

“ As in chemistry and physics, so in the science of living creatures there have been recent advances that have changed the whole prospect. A good instance is afforded by the discovery of the "hormones," or chemical messengers, which are produced by ductless glands, such as the thyroid, the supra-renal, and the pituitary, and are distributed throughout the body by the blood. ”

“ It is first dissolved by purely chemical processes, and the nutritive fluid is poured into the blood. Here it comes into contact with atmospheric oxygen admitted by the lungs. It unites with the oxygen as wood or coal might unite with it in a furnace. The matter-products of the union, if I may use the term, are the same in both cases, viz. carbonic acid and water. The force-products are also the same — heat within the body, or heat and work outside the body. Thus far every action of the organism belongs to the domain either of physics or of chemistry. ”

“ Accepting then the materialistic conception of the organism, we have to consider this further problem. Does the ground of organic processes lie in the whole organism or in its elementary parts? Translated into terms of metabolism—note the physiological point of view—the question runs, are metabolic processes the result of the molecular construction of the organism as a whole, or does the centre of metabolic activity lie in the cell? Is it the cell rather than the organism that is the immediate agent of assimilatory processes? ”

“ When those substances are wanting, whose function in the organism is to support the process of respiration, when the diseased organs are incapable of performing their proper function of producing these substances, when they have lost the power of transforming the food into that shape in which it may, by entering into combination with the oxygen of the air, protect the system from its influence, then, the substance of the organs themselves, the fat of the body, the substance of the muscles, the nerves, and the brain, are unavoidably consumed. ”

“ Since the sum of the chemical changes which take place in the animal is the breaking down of the highly-complex protein-molecules, derived from plants, into the simpler molecules of water, ammonia, and carbonic acid, it results that the potential energy thus set free is shown by the animal as "vital force," and the body of the animal is therefore a magazine or storehouse of force which may manifest itself as animal heat or light, or as sensible motion, or nervous disturbance ”

“ 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. ”

“ In this, but only in this sense, can these two conceptions be placed in opposition and used to characterize the processes in the living organism. The conception of the metabolism of stimulation must always stand in relation to that of an equilibrium of metabolism characterized by a constantly existing metabolism of rest, just as the conception of stimulus can likewise only be defined relatively to that of vital conditions. ”

“ The chemistry of the living cells—their anabolism, or how fresh material is built into their structure; their katabolism, or how the same structure is broken down that work may be done; in fact, the general metabolism—is so complicated, and so little understood as yet, and requires so extensive a knowledge of chemistry to follow, that it is best left alone by people who do not want to go into it deeply. ”

“ It is immaterial how the stimulus produces an excitating effect in the given case, whether through changes in the ion concentration of the living system, by increase of intramolecular atomic movement or in any other manner, it invariably accelerates the disintegration of the complex molecules concerned in functional metabolism, the nature of which varies in the special cases. In the great majority of instances nitrogen-free organic combinations serve as material for the functional constituent members of metabolic processes. ”

“ Every structure in the body in which any form of energy is manifested (heat, mechanical motion, chemical or electric action, etc.) is nitrogenous. The nerves, the muscles, the gland-cells, the floating cells in the various liquids, the semen, and the ovarian cells, are all nitrogenous. ”

“ THE BRAIN is made up of water, albumen, fat, phosphoric acid, osmazone, and salts.
THE LIVER unites water, fat, and albumen, with phosphoric and other acids, and lime, iron, soda, and potash.
THE LUNGS are formed of two substances: one like gelatine; another of the nature of caseine and albumen, fibrine, cholesterine, iron, water, soda, and various fatty and organic acids.
How these varied elements are held together, even science with all its deep searchings has never told. No man, by whatsoever combination of elements, has ever made a living plant, much less a living animal. ”

“ If the muscle is acted upon by functional stimuli, the excitation takes place mainly in the form of functional metabolism, nitrogen-free substances are broken down in increased quantities, whereas cytoplastic metabolism, which produces more profound alteration in the living substance, and which goes so far as to bring about a breaking down and building up of the nitrogen containing atom groups, is hardly at all increased. ”

“ In the animal body, as long as there is life, the processes of nutrition, of which I have already spoken, are going on, and in the course of these processes heat is constantly being evolved by chemical changes going on in the blood, which is the nourishing fluid. The oxygen gas breathed into our lungs is absorbed into the blood, it there meets with various compounds of carbon derived from the food, and uniting chemically with these gives off heat and produces the carbonic acid which we breathe out, as previously described. ”

“ A careful study of the conditions and processes necessary for both tissue building or nutrition, and tissue waste or disintegration, in all the higher order of animals, will show that neither process can be materially retarded without retarding or preventing the other. Both processes take place only in bioplasm or vitalized matter, supplied with oxygen, water and heat. Neither the assimilation of new material food, nor its use in tissue building can be effected without the presence of free oxygen and nuclein, or corpuscular elements of the blood. ”

“ All protoplasm absorbs oxygen when it comes in contact with it and in the process of combining with it is in part burned or oxidized, with the consequent setting free of heat and other forms of energy and the formation of carbon dioxide. So long as the body is alive, therefore, whether it is in a state of activity or of rest, it is the seat of constant chemical change throughout all its cells, and to these chemical changes are due all the forms of energy manifested by the body. ”

“ Your body is always giving out carbonic acid (Chemistry Primer, Exp. 7) . Your body is always giving out water by the lungs, as seen when you breathe on a glass, by the skin, and by the kidneys; and we shall see that we always give out more water than we take in as food or drink. Your body too is daily giving out by the kidneys and bowels, matters which are not exactly ashes, but very like them. ”

“ The blood is the principal fluid employed in distributing over the system the necessary elements of health and vigour, and for restoring the waste of the body. This fluid, in passing through the lungs, undergoes a very remarkable change, and not merely assumes a different colour, but [Pg 396] really acquires new properties, from its exposure to the air with which the cells of these organs are filled. By a true chemical process, the oxygen is separated from the air, that oxygen is made to combine with the carbon and hydrogen, and carbonic acid and water are formed. ”

“ In the study of metabolism and nutrition, both in health and in disease, in our conception of the anabolic processes of life, in our theories regarding the chemical relationships of the varied katabolites floating about through the organism and in many other connections, we need for our guidance a full knowledge of the chemical nature of this most important class of substances. ”