40 PHYSIOLOGY CHAP. 



some cases, having neither smell nor flavour, have no effect on the 

 sense of taste and smell. These are especially the senses which 

 evoke the digestive secretions and stimulate the whole nervous 

 system. Man does not live on food alone ; the pleasures of the 

 senses in moderation are necessary factors in his well-being, in his 

 physical and psychical life. 



XI. Inorganic aliments, such as water and mineral salts, are 

 just as necessary to normal metabolism as the organic. 



A large quantity of water is being lost continually through the 

 kidneys, lungs, and skin. It amounts on an average to about two 

 kgrnis. daily or 3 per cent of the weight of the body, when the 

 individual is in a state of rest and the equilibrium between the 

 intake and output of material is undisturbed, but is largely 

 increased during the performance of hard work. Water is there- 

 fore a most important factor in the exchange of material. 



Life without water or an adequate supply of water is impossible. 

 Thirst is more difficult to endure than hunger arising from 

 absolute deprivation of food. Disorders of the most serious kind 

 begin when the organism has lost 11 per cent of water, whereas 

 death from inanition only takes place after a decrease in weight of 

 40 per cent. When water is taken in quantities larger than are 

 necessary to cover the deficit, the surplus is eliminated mainly 

 by the kidneys, and with the water is discharged an increased 

 quantity usually about 3-5 per cent of the nitrogenous products 

 of combustion. When the water in the urine is three to six times 

 the normal average, the increase in the nitrogen contained in it 

 may be as much as 10 per cent. Thus if the current of water 

 passing through the organism be increased, the tissues are 

 cleansed from the nitrogenous products which they contain, and 

 the expulsion of urea from the circulating fluids is facilitated 

 (Voit), or the formation of it by the liver is increased, i.e. the 

 consumption of protein is increased (Bidder, Schmidt, J. Meyer). 



This increase in the consumption of nitrogen, caused by the 

 intake and discharge of very large quantities of water, persists in 

 animals which are fasting (Forster) ; whereas in animals which are 

 being fed it is merely transitory, and when the normal has been 

 reached it persists even if an excessive quantity of water still be 

 given (Neumann). 



Ortel's researches showed that the quantity of water introduced 

 into the organism also affected the accumulation and consumption 

 of fat in the body. When the loss of water in the excretions is 

 increased, when a smaller quantity is drunk, or, better still, when 

 the output is increased and the intake diminished at 'the same 

 time, it is always found that the fat accumulated in the body 

 decreases. This phenomenon has not yet been adequately ex- 

 plained, but, if it is a fact, it becomes of practical importance in 

 the cure of obesity. 



