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 Life is usually seen as a continuous process. It arises at the moment of the emergence of a living being in an egg, a spore or a seed, goes through a number of more or less complex stages of development, reaches a certain flowering, decreases with aging and ends at the moment of old age, when all life processes stop.
We know, however, the phenomenon of oppression of life, when life temporarily freezes in the body and life processes are more or less suppressed. Such phenomena include sleep, normal and pathological (hypnosis), anesthesia (when the body is exposed to chloroform, ether, etc.), and finally, hibernation, which is known in many animals. In all these cases, however, there is not a complete suspension of life processes - movements stop, sensitivity significantly weakens and almost disappears, but metabolic processes remain, the animal does not stop breathing, its organs are still supplied with blood, the intestines continue to digest food. In a state of hibernation, all these processes are greatly slowed down, but still they do not stop completely.
We also know the phenomenon of the hidden life of seeds, spores, and animal eggs. A seed is an immovable object, seemingly dead, life does not manifest itself in it, but it is worth putting it in certain conditions of humidity and temperature, and violent processes of life awaken in it. However, even in a dormant state, under normal storage conditions, some very weak life processes, or at least some chemical changes, apparently occur inside the seeds. Therefore, seeds cannot be stored forever.
Eggs of animals are less hardy, even in those cases when they are specially adapted for long-term storage, for example, in daphnia. Two to three decades are still the maximum pot life during storage. It is clear that here in the eggs, as in the seeds, some weak processes are taking place that change the living being.
But if life processes can be so suppressed and reduced that they become completely invisible, then is it possible to stop them for a while with the help of external influences? Is it possible to interrupt life so that it then comes back again?
 As early as 1701, a discovery was made that seemed to give an affirmative answer to this question. The famous Dutch amateur microscopist Anton Leeuwenhoek examined sand, which he collected in the gutter of the roof of his house in Delft, with the help of his own primitive, but already quite well-magnified microscope. For this purpose, he put a small amount of perfectly dry sand in a glass tube filled with water. Examining it under a microscope, he noticed the appearance in the water of some tiny "insects" that swam quickly with the help of "wheels", that is, the crowns of cilia on the head.
This phenomenon interested him, all the more since by experiments he established that "insects" are taken from dry sand and not from water, and further experiments showed that they can again be dried together with the sand - they shrink and turn into tiny lumps, indistinguishable from grains of sand. In dry form, together with sand, Levenguk kept these animals, later called rotifers, at first for several weeks, then for several months or even more than a year, and from time to time revived them by placing them in water. They came to life quite quickly and swam briskly, as if nothing had happened, until the water dried up. He reported this remarkable discovery of his to a letter to the Royal Society of London, in the minutes of which it was later published, but apparently little attention was paid to him at that time.
Only later, in the second half of the 18th century, these experiments of “miraculous resurrection from the dead” of dried rotifers aroused the interest of scientists. Around the same time, another famous scientist, Spallanzani, professor of physics and natural history at the University of Pavia, investigated this phenomenon in detail, making many experiments and observations. He found that rotifers can dry up and revive up to eleven times in a row, that the presence of sand is important for their successful revival, which makes drying more gradual, and that when dried they can tolerate such high temperatures (54-56 ° C) at which, being in the water, they die.
In addition, he discovered another group of creatures that have exactly the same drying and revitalization abilities as rotifers - these were microscopic small creatures, similar to caterpillars, living in the moss growing on the roof. For their slow movements, he called them tardigrades, and this name has remained for them to this day.
Later it turned out that another group of inhabitants of mosses and lichens behaves in exactly the same way - these are small roundworms of a nematode. All these animals are specially adapted to drying out, just like the moss or lichen in which they live are adapted to this. Under the burning rays of the sun and under the action of a dry wind, they all dry out, shrink, turn into light specks of dust carried by the wind. As soon as; however, dew or rain will moisten the moss, they swell, straighten and come to life.
It is interesting that already in those days, at the very discovery of the phenomenon of the revival of apparently dead animals, two opposite points of view were established on its essence. Levenguk believed that rotifers do not dry out completely, since their shells are so dense that they do not allow water to evaporate completely. Therefore, their life does not end completely, but only weakens, and then flares up again, and they come to life. In contrast, Spallanzani believed that when dried out, life actually ceases, and then the animals are resurrected. He recognized, therefore, a real cessation of life, a complete interruption of it.
Later, in the 19th century, these two diametrically opposed views of revival continued to exist simultaneously in science. Some researchers, however, tried to deny the very phenomenon of revival, and among them, the famous German microscopist and researcher ciliates Ehrenberg spoke out with particular insistence against revival. He argued that rotifers in the sand in a dried state not only feed, but also reproduce, lay eggs, and that their revival depends simply on the fact that they have acquired the habit of living with more or less moisture.
 Extremely carefully staged experimental studies of the French biologists Dwyer, Davain and Gavarre, the results of which were verified and confirmed by a special commission of the Paris Biological Society, chaired by the famous Brock (1860), convinced the scientific world of the validity of the observations of Levenguk and Spallanzani. Brock's commission spoke in favor of the possibility of complete drying and for a complete stop of life. “At the present time,” says Broca, “there are two teachings: one recognizes revival as a vital phenomenon, the other as a phenomenon independent of life, conditioned exclusively by the material aspect of a living being. The first teaching is "in complete contradiction with the results of drying experiments, the second, on the contrary, not only does not contradict them, but even allows one to explain the basic drying experience and all other experiments."
Such prominent scientists as Claude Bernard, Wilhelm Preyer, and later - Max Vervorn joined the opinion about the possibility of temporarily interrupting life. Preyer in 1873 proposed a special term for the whole phenomenon of revival - anabiosis (from the Greek ava - upwards and - life, - "revival", "resurrection"), which then became firmly established in science.Until recently, most of the researchers involved in the organization of experiments on suspended animation (they stood, however, on the opposite point of view - they did not manage to create such conditions under which the cessation of life would be obvious and, nevertheless, revival would occur. Therefore, the conviction was created that life does not completely stop when drying out, that in dried animals that have not lost all the water contained in them, some, even very weak, muffled life processes still proceed, there is a minimum life (vita minima). Of course, the latest researchers did not fall into such a mistake as Ehrenberg, and did not assert that dried rotifers feed and reproduce, but the presence of some metabolism in them, in the form of at least slow motor processes, could be assumed, since they have residues of water in the surrounding the atmosphere contains oxygen.
To prove the possibility of stopping life, it was necessary to deprive the dried animals of all the free water contained in them, not chemically bound, and to stop breathing. Brock's commission also established that moss with dried animals can be heated to the boiling point of water for half an hour and, nevertheless, rotifers come to life. Such strong drying, however, is nevertheless associated with a risk to the life of the dried animals. The authors of these lines were given a more cautious drying experiment in 1920. The moss with the rotifers dried in air over calcium chloride was placed in a test tube, which, in addition, contained a piece of metallic sodium to absorb the remaining oxygen and moisture. Air was evacuated from this test tube with a mercury pump until a vacuum with a pressure of 0.2 mm was obtained, and the tube was then sealed. After storing the moss in it for several months, the rotifers, which were gradually transferred to water, came to life, despite such a long stay in a vacuum without oxygen and with complete dryness.
The Austrian scientist Dr. G. Ram managed to deliver in 1920-22. a series of even more convincing and effective experiments.
First of all, he set up an experiment of storing moss in a vacuum, quite similar to mine (but without the use of sodium), and with exactly the same results.
Then he transferred his work to the famous laboratory of low temperatures prof. Kammerling Onnes in Leiden (Holland), where it was possible to use any gases in a liquid state. There he set up an experiment in drying moss with rotifers and tardigrades in inactive gases. The moss was placed in a tube that was filled with absolutely dry hydrogen or helium obtained from liquefied gas. Then this gas was pumped out by a mercury pump to the fullest possible vacuum, then it was let in again and pumped out again. After three such manipulations, the tube was sealed and stored for a more or less long time. After opening it, the animals revived in the water.
 For even more complete drying, Ram built an apparatus. The moss was placed in a glass ball, into which this gas was supplied from a vessel with liquid hydrogen, and on its way it passed through a coil placed in liquid air; thanks to cooling, the last remnants of the moisture extracted from the moss settled there. The tube was connected to a mercury pump, which gave the maximum vacuum. A light bulb was connected to the same tube as a control apparatus to monitor the vacuum. On the other hand (right), the ball communicated with several test tubes, into which the moss could be poured at the end of the experiment. To remove the adsorbed air from these test tubes, as if adhering to their walls, they were heated to 300 ° C in an electric oven during the experiment. As in the previous experiment, hydrogen was injected into the ball and pumped out several times. A special feature of this experiment, however, was that the ball was heated to 70 ° C for more perfect drying.This temperature is as established by the control! experiments, does not have a harmful effect on dried animals. After this drying procedure, the moss was poured into chilled test tubes by tilting the tube and sealed in them. These tubes were stored and opened at different times, from one to eight months. The animals contained in them came to life.
Finally, in addition to drying, Ram exposed the animals to extremely low temperatures, namely from -269 ° to -272.8 ° C, in other words, a temperature that is only 0.2 ° C higher than absolute zero (-273 ° C), i.e. that is, the minimum theoretically possible temperature. In all these cases, the result was the same: after careful and gradual thawing, the dried animals revived after being transferred to water.
What do these Rama experiences tell us? Drying the animals with absolutely dry gases (hydrogen, helium) that do not support breathing and easily penetrate the shells, when pumped out to a full vacuum and some more heating, of course, should remove all free water from the body. Adsorbed water is unlikely to remain under these conditions. In the complete absence of oxygen and water, it is difficult to imagine that any breathing processes could take place - all gas exchange in the body must stop. But, if in this case it is still possible to talk about some anaerobic (i.e., occurring without the presence of air) or intramolecular metabolic processes that are possible in the body, then when using low temperatures close to absolute kul, no what metabolic processes can not be discussed. Indeed, under these conditions, at the temperature of liquid helium, no chemical reactions are possible at all, and all the less, of course, reactions as subtle as those occurring in the body are possible - they require the participation of water, colloids, gases, salts, enzymes, require great mobility of chemical particles. In conditions close to absolute zero, all chemical molecules lose their mobility. Not only all liquids, but also gases pass into a solid state, colloids and, in general, all compounds containing at least chemically bound water become solid like a stone. The body of a dried rotifer under these conditions hardly differs greatly in its chemical activity from a quartz grain.
Thus, we must admit that under the conditions of these experiments, the dried inhabitants of the mosses completely lost all, even the smallest, manifestations of life processes. What kind of life is possible in a piece of solid stone? And if then, after thawing and the addition of water, life returned to them, then this means first of all that, but in ka life is possible, life can be interrupted - it is not always a continuous process.
Understanding the reasons for this phenomenon, we see that the possibility of the return of life to an organism deprived of water and, moreover, subjected to the action of extremely low temperatures, is conceivable only if all these destructive effects do not destroy living matter, do not produce such changes in it that would be, as chemists say, irreversible. Indeed, if we dry gelatinous silicic acid - an inorganic substance, which is the same colloidal solution as most of the constituent parts of a living organism, we will see that it can be dried to a certain limit so that it will only thicken, but will not change. It is necessary to add water to it again, and it will again turn into liquid jelly. If, however, this limit is crossed, the jelly will become hard, opaque, and no amount of water can return it to its previous state - the silicic acid has undergone irreversible changes from excessive drying. The same thing happens with a living being.
Research carried out over the past 10-15 years has shown that many animals can be subjected to very severe drying.So, by drying earthworms, it is possible to extract from them, according to my experiments and Hull's, about 3/8 of all the water they contain.
Japanese turtle leeches that crawl ashore and bask in the sun for a long time can dry out to the point that they lose 80% of their weight.
I was able to dry young frogs and toads to the point of losing half of all the water contained in the body. Prof. BD Morozov dried various organs and tissues of animals to the point of losing 1/4, 1/2 or even 3/4 of water, and they did not lose their vitality. In all these cases, drying is possible only up to a certain limit, followed by irreversible changes in living matter and death.
In the inhabitants of mosses and lichens, this ability of drying is brought to extreme limits. Through long evolution, it has developed in them as an adaptation to their daily life. Their habitat is periodically subjected to strong drying under the burning rays of the sun, or wetting by rain, dew or fog. If he did not have the ability to dry out, their death would be inevitable. And now the living colloids of their bodies have acquired the ability to freely give up all the water they contain, without undergoing such irreversible changes that would put their lives in danger. Under natural conditions, however, this drying is never complete, but under experimental conditions, it is obvious that it can be brought to the loss of all free water. In the absence of water, low temperatures, close to absolute zero, turn out to be harmless.
We have here, therefore, one of the most remarkable cases of adaptation to the external environment, an adaptation that affects not in the development of any organs or form features, but in a change in the entire structure of living matter, in the acquisition of completely extraordinary abilities by the latter.
Is this case one of a kind? Not at all. We need to recall only those cases of hidden life widespread in the plant and animal kingdom, which we spoke about above. Indeed, even there, in the seeds and cysts of animals, the same adaptation of living matter to drying out and to a prolonged stay in a dried state occurs.
 And if, under natural conditions, seeds and spores are not absolutely dry and always contain several percent of water, then, one must think, it is this circumstance that causes in them those slow, poorly expressed metabolic processes, which in the end entail weakening and disappearance viability of seeds. Until recently, the theory of "minimal life" also dominated in science regarding seeds and disputes. It was assumed that life in them does not stop, but only comes down to the most minimal manifestations of gas exchange and to the processes of metabolism associated with them. The experiments of Becquerel on seeds and McFadane on spores of microorganisms showed that here, under the experimental conditions, a complete cessation of life is possible - a break in life is possible.
Becquerel subjected the seeds of various plants to artificial drying in a vacuum when heated to 40 ° C, kept them in a vacuum for 4 months and then placed them for 10 hours in liquid helium, which gave a temperature of - 269 ° C. When germinating such seeds, it was found that they germinate even better than the control ones stored in vivo - so clover seeds germinated all, while only 90% of the control ones germinated.
Similar experiments were carried out by Becquerel on the spores of ferns and mosses and by McFadane on the spores of various bacteria and cocci; in all these cases, vigorous drying in a vacuum and temperatures close to zero stopped all life processes, made the manifestations of even the most reduced metabolic reactions during hours and days inconceivable. Nevertheless, after the elimination of these retarding conditions, life returned to the body and came into its own.
Becquerel rightly says that under the conditions of these experiments protoplasm becomes harder than granite and although it does not lose its colloidal nature, it loses the state that is necessary for assimilation and dissimilation. If the cell is deprived of water and basins, which have passed into a solid state, if its enzymes are dried and the protoplasm has ceased to be in the state of a colloidal solution, it is clear that in this case one can hardly speak of a "slowing down of life." Life without water, without air, without colloidal particles suspended in a liquid medium is impossible - under these particular conditions, it was possible to achieve a real "hidden life" in the sense of Claude Bernard, that is, a complete cessation of life.
So, stopping life, interrupting the life process under certain conditions are possible.
P. Yu. Schmidt
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