732 Water in Relation to Health and Disease. 
Of the large amount of water contained in the organism of 
the higher animals nearly the whole enters by the mouth, either 
in a free liquid condition or in combination with the various 
foodstuffs. That a certain quantity is actually formed in the 
body itself is made clear by the fact that the total amount 
which passes out of it in the twenty-four hours is greater than 
that which passes into it. If the quantity exhaled by the skin 
and lungs be added to the still greater instalment excreted by 
the kidneys, bowels, and other organs, the sum of the whole 
exceeds the quantity ingested. How this additional amount of 
water is formed in the system may be understood by consider- 
ing those changes which are constantly taking place as the 
result of the action of oxygen on the hydrocarbons of the food. 
In this connection it may be noticed that a process of slow 
combustion is constantly going on in the tissues of the body, 
during which the carbon of the food by uniting with the 
oxygen of the air produces carbonic acid, while the hydrogen 
which remains combines with other portions of oxygen to form 
the water referred to. 
As we have just now seen, water enters largely into the com- 
position of all the secretions and excretions of the body, and 
serves as a medium through which the active principles of the 
former are enabled to exercise their influence in the various 
functions of life, while it also serves to convey from the system 
the waste materials which naturally result from the wear 
and tear of the flesh, and which if retained would poison the 
blood, and sooner or later end in disease and death. Urine 
and bile are good examples of water bearing away effete matters 
of the kind referred to. All the organic constituents of food, 
whether they be carbohydrates, hydrocarbons, or albuminoids, 
as well as the various mineral salts, oxides, &c., must undergo 
solution or emulsification before they can be made use of in the 
nourishment of the tissues. The initial stage in the process of 
digestion, by which the food is broken down into a pulpy mass 
by the teeth, is dependent for its efficiency upon the moisture 
furnished by the saliva. Moreover the water contained in this 
secretion, aided by that taken into the stomach for alimentary 
purposes, serves to dissolve the food after it has undergone 
the necessary chemical changes which result from t)ie action 
of the digestive juices. The digestive juices themselves are 
for the most part water. In 1,000 parts of gastric juice there 
are 973 parts of this fluid, in bile 864, and in saliva as much 
as 995. 
The blood itself contains 791 parts of water in 1,000, and 
its power to circulate through the system, and to give out from 
