( Originally Published 1913 )
Like the plant, man cannot live without water. A plant may have at its disposal ever so much of the nutritive salts, without which it cannot live, but they are of no use to it unless it receives water, be this rainwater or dew, or that provided by the helping hand of man ; water is absolutely required to bring these salts in solution, so that they may be absorbed by the roots. Man, likewise, would not be able to assimilate his food without water, since it dissolves the nutritive substances, that they may be taken up by his body. The digestive fluids require a considerable amount of water, as does also the blood, of which it forms the most voluminous constituent. Through the aid of the water, the nutritive substances and salts which have been dissolved are carried from the blood into the tissues. For this a sufficient quantity of water must be at the disposal of the blood; if the blood receives too much of it, on the other hand, it will become too dilute. However, all-wise Nature has made provision for this eventuality—just as she has taken great care in the creation of man in general, much more than has been expended upon any machine devised and constructed by man himself—through the fact that this diluted condition is only a temporary one, soon disappearing. When too, much water is withdrawn from the blood by copious diarrhea, as in cholera, or through excessive perspiration or a diet containing too little water, the blood may become thickened; Grawitz, however, has shown that this condition is also merely a temporary one ; the inspissation soon passes off as a large amount of fluid is again taken up by the tissues.
While the absorption, then, of large quantities of water cannot cause any lasting effect, it is nevertheless not desirable to ingest too much of it, say, more than 1 1/2 liters per day, since the tissues would then become too watery, and the task of the blood-vessels and heart be rendered too difficult through their being overloaded with so much fluid. In persons in whom the heart or the vessels are affected, as in heart disease or arteriosclerosis, this may bring about serious results, and consequently such persons should never take more fluid, soup and milk included, than 1 to 1 1/2 liters daily. For these patients the best way of taking fluids is in the form of fruit and fresh green vegetables ; in this way water is absorbed, albeit very gradually, so that there is no sudden overloading of the vessels and the heart is not taxed with too much work.
Grawitz, on the contrary, is of the opinion that large amounts of fluid do not have a lasting influence, either on the composition of the blood or that of the gastric juice. When much water is taken with the meals, the acidity of the gastric juice may be diminished for a short time, but it is soon restored to the normal condition, and, in regard to drinking while eating, I am personally of the opinion that it is a hygienic practice ; a swallow of water, as Pawlow has shown, exerts a favorable influence upon the secretion of the "appetite juice," or psychic secretion of the gastric fluids, and many persons have no appetite for their food if they cannot at the same time take water or other fluids. I consider that even a little too much water taken with the meals is less injurious than the avoidance of it altogether. A great many women have the very bad habit of not drinking at all while eating, owing to a mistaken idea that this will keep them from growing stout. Now, water-drinking never causes the production of fat, as has been demonstrated by von Noorden. On the contrary, with the help of the water the nutritive substances are much better assimilated, while the appetite, as we have just said, is in-creased. Another great advantage is that the bowel functions may be assisted, and this, precisely, in women, who suffer from their wrong and avoidable habit of constipation, is greatly to be desired. 'When the contents of the intestines are well supplied with water, the forward movement of the feces is greatly facilitated. One of the very great advantages of drinking water is the fact that the end-products of the metabolic process are washed out, and this is more fully accomplished the more water is taken. While we thus consider the drinking of water as a very healthy practice, we must, on the other hand, not forget to mention that the drinking-water itself may some-times be dangerous, even to life, when its origin is not unquestionable. The best drinking-water is furnished by mountain springs ; it does not contain any germs. It is owing to this that Vienna is much less affected than almost any other large city in the world by typhoid fever, which is so frequently caused by impure water. The water system of Vienna, which brings the water from afar, cost millions, but probably millions were never spent to better advantage, or have never borne better fruit. On the other hand, we very frequently meet this disease, which so often destroys young lives, in all cities which are supplied with river or fountain water. In addition to the purity of the drinking-water, its chemical properties are also most important. According to Roese's examinations, the health of a population is enormously influenced by the composition of its water supply. Not only does hard drinking-water have a most beneficial influence upon the teeth, but in cities where such water is drunk the chest measure and height of the people is greater, as well as their fitness for military service, while where the water is soft the opposite condition prevails. Moreover, the hard water has a more refreshing taste, which is quite an important advantage. In regions where the water does not have an agreeable taste, or is not free from impurities, the use of a not too highly mineralized water is advisable. The mineral waters containing some carbonic acid are more refreshing and also excite the appetite, especially in hot weather, when the mouth feels dry. Slightly mineralized waters are well fitted for daily use all the year round. This applies in a less degree, however, to those containing a considerable quantity of salts, which are really to be considered as medicinal waters, and are best used, for any length of time, in chronic diseased conditions.