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VETERINAEY HYGIENE 



opening being protected by a louvred cover. Such tubes 

 may be fixed in the roof of the stable, but are far too un- 

 certain in their action. 



Another form of divided tube is McKinnell's (Fig. 18). 

 This consists of two circular tubes, one placed within the 

 other. The area of the outer tube should be larger than 

 that of the inner, as there is double friction to be over- 



come. 



The inner tube is the outlet, the air in it being kept 

 warmer by the outer tube ; outside the building it is carried 

 higher than the latter, and surrounded by a hood, though 



—J f\ 



/ 



Fig. 17.— Divided tube 

 (Pavkes). 



Fig. 18.— McKinnell's tube 

 (Parkes). 



a cowl would be preferable. Where the inlet tube enters 

 the room is a flange to prevent down-draught and dis- 

 tribute the air. 



When the doors of the stable are open both inner and 

 outer tubes become outlets, when the door is closed the 

 double action of the tube is again established. 



As a means of ventilation for a small stable it is un- 

 objectionable. 



Tobin's tubes (Pig. 19) are sometimes used as inlets in 

 the ventilation of stables. The tube, which is about six feet 

 high, is placed against the inside wall, while externally it 

 is carried through the wall at the ground level. The air 



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