90 



VETERINARY HYGIENE 



have to be admitted per hour, the rate of exchange of the whole 

 air in the box would be much slower, namely, seven and a half 

 times per hour, or once in every eight minutes. 



Experience has led to the belief that people in this country 

 cannot stand the air being changed more frequently than three 

 times per hour, and on this, accordingly, is based the 1000 cubic feet 

 of space thought to be necessary for each adult person. A great 

 deal depends, however, on the cooling power of the air. 



Experience has shown likewise that horses and cattle can stand 

 the air being changed as frequently as nine times in the hour without 

 any discomfort or ill effects. Mackenzie and Russel are of the 

 opinion that fowls should not be expected to contend with a more 

 frequent change than four times each hour. It is probable that pigs, 

 dogs, calves and sheep can stand the air being changed as frequently 

 as can horses and cattle. In accordance with this conception the 

 table here appended has been compiled. 



Table showing the amount of fresh air required each hour and 

 the necessary cubic space per animal : 



GENERAL PRINCIPLES OF VENTILATION. Ventilation means the 

 methodical and uninterrupted exchange of foul for fresh air, so that 

 at no time does atmospheric pollution in a building exceed a given 

 standard. 



If a number of cows are housed during the night in a byre 

 the windows and ventilators of which are all closed, by the morning, 

 when the cows are turned out to graze, the air in the byre will have 

 become extremely foul. If after the animals have left the building 



