254 THE HORSE IN SERVICE 



of the wind. Outlets are usually provided at the ridge pole, 

 by direct flues from below or by an open ceiling. 



The King system of ventilation is to be recommended when- 

 ever its installation is practicable. It is made up of two kinds of 

 flues: (1) Those for intake of fresh air, and (2) those for the 

 outtake of foul air. The intake flues start at a point two feet or 

 more above the ground outside and extend to the inside near the 

 ceiling. The outtake flues start near the floor of the barn and ex- 

 tend above the highest point of the roof. 



Fresh Air Requirements. — The fresh air and cubic space 

 requirements per horse should be considered in the construction 

 of stables and the provision of windows. It has been estimated 

 that a horse of average size requires approximately 15,000 cubic 

 feet of fresh air per hour, and this is the ideal aimed at in the 

 English Army. Col. Fred Smith in his book on Veterinary Hy- 

 giene describes a simple method of arriving at the horse's fresh air 

 requirements and of determining whether or not these require- 

 ments are being met. He bases his conclusions on the fact that 

 the horse inspires about 100 cubic feet of air per hour while in 

 the stable, and his expirations completely vitiate air, to the ex- 

 tent that it would not sustain the life of a mouse, at the rate of 

 twenty- five cubic feet per hour. This air requires a dilution of 

 150 times in order not to be injurious when rebreathed as it 

 would be in the ordinary stable. De Chaumont's test makes it 

 very simple to detect an injurious amount of respiratory impurity 

 in the air. By actual analysis it has been determined that the 

 sense of smell upon first entering the stable from the outside may 

 be relied upon, not only to detect but to gauge the amount of res- 

 piratory impurities present. An amount up to .2 per thousand 

 may be present without being perceptible; .4 per thousand gives 

 to the air a smell suggested by the term " rather close " ; .67 per 

 thousand "close"; .9 per thousand "very close — offensive." 

 Therefore, it is concluded that sufficient vitiation to be detected 

 by smell renders the air unfit to be breathed and .2 per thousand 

 has been taken as a standard of requirement. By the equation 



Amount of carbonic acid exhaled per hour ( Fresh air required, 15,000 



;^ -. — TTi -. — : rr. = { cubic feet per hour is de- 



The permissible organic impurities ( termined to be necessary. 



