134 SCIENCE PRIMERS. [§ viii. 



when it moulders away either above ground 

 or in the soil, whether it be quickly oxidized 

 by living arterial blood while still alive — in 

 all these several ways the things into which 

 it is burnt, into which it is oxidized, are the 

 same. Whatever be the steps, the end is 

 always water, carbonic acid, ammonia, and 

 salts. 



These are the things which are always being formed 

 in the blood through the oxidation of the body, these 

 are the things of which the body has always to be 

 getting rid. 



In addition to the water which comes from the 

 oxidation of the solids of the body, we are always 

 taking in an immense quantity of water; partly because 

 it is absolutely necessary that our bodies within should 

 be kept continually moist, partly because food can- 

 not pass into the blood except when dissolved in 

 water, and partly because we need washing inside 

 quite as much as outside; if we had not, so to 

 speak", a stream of water continually passing through 

 our bodies to wash away all impurities, we should 

 soon be choked, just as an engine is choked with soot 

 and ashes if it be not properly cleaned. We have, 

 then, to get rid daily of a large quantity of washing 

 water over and above that which comes from the 

 burning of the hydrogen of our food. 



We have already seen that a great deal of the car- 

 bonic acid goes out by the lungs at the same time, 

 that the oxygen comes in. A large quantity of water 

 escapes by the same channel. You very well know 

 that however dry the air you breathe, it comes out of 

 your body quite wet with water. 



