164 POULTRY CULTURE 



constant tearing down and building up, which means a con- 

 stant supply of oxygen from the air by way of the lungs and 

 the circulation and a return of a poisonous gas, carbon dioxid, 

 by the reverse route, lest the bird dies of oxygen starvation 

 and carbon dioxid poisoning. 



The body then is a great oxidizing apparatus and must 

 have a constant and abundant supply; hence ample ventila- 

 tion of all types of poultry houses is imperative. 



Air is a mechanical mixture of three gases — -namely, oxygen, 

 nitrogen, and carbon dioxid, with traces of other gases, as 

 ozone, ammonia, argon, and bacteria, and other impurities that 

 chance to be floating in the air. The usual accepted formula 

 of air is as follows: 



Nitrogen 78 . 00 per cent. 



Oxygen 20.96 



Argon 1.00 '' 



Carbon dioxid .04 " 



100.00 



Air has a tendency to be purified by washing in time of 

 rain. 



Plants utilize the carbon dioxid from the air as plant food 

 and is used in the construction or building up of starch in the 

 plant, and in return the plant gives off to the air oxygen as a 

 by-product in this starch construction. 



Since oxygen supports combustion in the body it is a con- 

 stant and essential element. 



When the air contains as great an amount of carbon dioxid 

 as 5 to 10 per cent, it becomes poisonous, hence ill effects in 

 improperly ventilated brooder houses and incubator rooms, as 

 well as rooms for other kind of bu'ds. 



The earth contains two hundred and fifty times more carbon 

 dioxid gas than the atmosphere. 



During dry, dusty, and windy times there may be consider- 

 able organic and inorganic matter in the atmosphere. These 

 dust particles contain germs, some of which may be germs 

 of disease, and this is one way contagious diseases are spread. 

 The infected dirt particles are blown from an infected yard to 

 other premises by the wind. 



