AIR AND VENTILATION 83 



be too low the health of the animals will suffer and unhealthy cows 

 cannot produce healthy milk. This being so, no degree of vitiation 

 ought to be permitted that will prejudice the health of the con- 

 fined animals, whatever the financial problem might be. 



Notwithstanding that Hendrick did once find a cow byre con- 

 taining no greater amount of CO 2 than that which has been defined 

 above as permissible, the author is inclined to think that this 

 standard is in general almost unattainable and, in the case of 

 herbivorous animals, hardly necessary. It is here suggested that 

 the limit of CO 2 impurity should be 0-06 per cent, for all animal 

 habitations, that is to say, the total proportion of CO 2 in the air 

 should not exceed 0-09 per cent. 



Undoubtedly the chief significance of carbon dioxide in a build- 

 ing is the general indication it may afford of the efficiency of the 

 ventilation. In habitations devoid of artificial heating, excessive 

 humidity and high temperature are the chief evils; both are con- 

 comitant with air stagnation. Air stagnation in an inhabited 

 building necessarily means an increase in the proportion of CO 2 , 

 and though it is rather doubtful in the case of herbivorous animals 

 if the percentage of this gas really affords an exact indication of 

 the degree of vitiation, it is certain that if it is not present in 

 greater amount than 0-05 per cent, the state of the atmosphere 

 will be all that could be wished for. It is believed that if 0-09 

 per cent, be present no harm will result, and that neither tempera- 

 ture nor humidity will be greater than is desirable. Never- 

 theless it is an indisputable fact that the nearer to natural con- 

 ditions animals can be kept the healthier will they be. There is 

 also unquestionable evidence that horses can live and thrive in open 

 stables in this country throughout the winter, being merely sheltered 

 from wind and rain. Under such open-air conditions infectious 

 diseases are rare, and when they do occur are of a benign type. 



INCREASE OF HEAT AND HUMIDITY. When a number of animals 

 is confined in a building where inadequate provision is made for 

 ventilation, the temperature of the air rises from the heat given off 

 from their bodies. As the temperature of the air increases by 

 the accumulation of this thrown-off body heat, so is there an increase 

 in the amount of CO 2 , organic matter and water vapour, and a 

 corresponding decrease in the amount of available oxygen. 



The difference between the temperature inside and outside an 

 animal building, where no artificial heating is employed, is a good 

 guide to the general condition of the air. If in the winter the 

 difference is not great then it may rightly be assumed that the pol- 

 lution is not excessive and, on the contrary, if the inside temperature 



