228 THE PRINCIPLES OF AGRICULTURE 



under such conditions. The amount also varies 

 with the kind of animal. The pig produces 

 more in proportion to his body weight than 

 the carnivora, rabbit, and fowl ; and these 

 again produce a larger proportionate amount 

 than the horse or the ox. 



420. Air which contains 10 to 12 per cent 

 of carbon dioxid will no longer sustain life. The 

 deleterious effect is due partly to the lack of 

 oxygen in such re- breathed air, but also to the 

 excess of the poisonous carbon dioxid, volatile 

 organic matter, and other injurious products. 

 Air which contains even 1 per cent of carbon 

 dioxid produced by breathing is injurious to a 

 marked degree. In a perfectly close place, 

 where there can be no access of fresh air, a 

 horse would contaminate to this extent over 7,000 

 cubic feet in 24 hours. 



421. The question of stable space, however, is 

 dependent on the amount of air that can be 

 introduced by ventilation in a given length of 

 time. The tighter the building and the less the 

 admission of fresh air, the greater must be the 

 area supplied ; while the greater the facility for 

 the entrance of fresh air, the smaller need be the 

 space per animal. If the whole of the air could 

 be removed every three hours, 1,000 cubic feet 

 per horse or cow would suffice to keep the air 

 sufficiently pure and wholesome. 



