HEREDITY AND AIR. 87 



Nitrogen is nearly negative in effect. It dilutes oxygen and 

 CO2. 



Ammonia in air must also be regarded as an impurity so far 

 as animal life is concerned, mainly because of the organic mat- 

 ters with which it associates. Such organic matters adhere to 

 ceiling, walls, harness, floors, etc. 



Ventilation. — Ventilation, therefore, is very important and 

 should be thorough. Accomplishes two purposes : admits oxy- 

 gen, dilutes and removes impurities. Good ventilation implies 

 rapid change in air of the stable without direct draughts upon 

 confined animals. Each mature cow or horse should have about 

 1,500 cubic feet of air and this should be renewed frequently 

 (see lecture on ventilation). 



Sunshine is equally important, for sunshine is nature's uni- 

 versal disinfectant, killing more or less rapidly germs of disease 



