Water losses of a living creature are difficult to take into consideration, their average sizes have only definitions, and the exact ones are different for everyone. It is well known, for example, that each of us sweat in his own way in the same conditions. The losses of water at breathing make on the average about 4*102 g. The losses from a surface of skin, connected substantially with thermoregulation, vary, but on the average make 6*102 g. The direct losses are between (1-1,5)*103 g.All these losses are made within one day, therefore, the general daily losses make (2-2,5)*103 g of water.
The losses of water result in thirst. The man satisfy it as with direct consumption of water, as through food containing water. But how does the thirst appear? All components " of internal hydrosphere " in balance are among themselves. If the concentration of the dissolved salts in blood, in interstitial liquid or inside cells rises, than the water is provided to them through the biological membranes of cells. The main work of cells-receptors, signaling on reduction of water in the organism, is based on moving of water through a half-permeable membrane from a less concentrated solution to more concentrated. These crates - the centers of thirst, or centers of regulation of internal hydrosphere - are in hypothalamus together with the centers of famine, thermoregulation and some other. When contents of salts around cells-receptors grows, water leaves them and they are slightly compressed. It is enough for appearing of feeling of thirst. The damage of the appropriate site of hypothalamus can cause a constant thirst or, on the contrary, an absence of interest to water even then, when the mouth dries up from thirst. There are also the other apparatuses, signaling of thirst. They arise also at the large loss of blood, but telling the truth, it is necessary, that the losses exceeded 10 % from weight of blood. The feeling of thirst thus arises not at once, but after some hours. Such delay can be even useful, as, for example, in the morning, when we rise from bed, about 10 % of blood casts to legs and, if there was no delay of a signal of thirst, the man would feel thirst at each such the change of a position. It is interesting, that the cosmonauts consume less waters in weightlessness, when blood is allocated in order (regular intervals), than on the Earth, and it means, that there is a part of water, we consume as a debt to walking straightly, with all following from it consequences. The part of water is formed directly in the organism at disintegration of fibers, of fats and carbohydrates, it is a so-called endogenous water. So, at oxidation 100g of fats 107 g of water is formed, and the oxidation 100 g of carbohydrates gives 55,5g of water. There are animals, consuming generally only that water, which is formed inside of the organism. In the driest deserts, where, apparently, there can be nothing alive, there are small beetles, living in a ground, which eat the rests of plants, brought from apart by a wind, extracting water from them in a processing of organic substances, contained in these rests. Rodents, eating grains, require no drinks. Such the animal, as camel, reserves water beforehand in a fatty hump, the complete oxidation of which can give up to 40l of water.
