62 VETEEINAEY HYGIENE 



ventilation, and it is fortunate for the animals their 

 artificial life is only a matter of a few months. 



It is quite useless to plead for better conditions, when 

 men's pockets are touched with no corresponding return.* 



THE METHODS BY WHICH FRESH AIR CAN BE 

 SUPPLIED. 



Natural Fcntifoiio)?.— Ventilation is of two kinds, natural 

 and artificial ; in veterinary hygiene it is the former which 

 principally concerns us, and this is brought about through 

 three agencies : — 



1. The process of diffusion. 



2. The action of the winds. 



3. The difference in weight of masses of air of un- 



equal temperature. 



Natural ventilation can only be effectively employed 

 when the type of building is such that the above forces can 

 come into operation. 



This type of building may be briefly described as one 

 where the animals are arranged in two rows only, the 

 heads turned to the outside walls. The width of the 

 stable should not exceed thirty feet, and only two animals 

 placed between opposite sources of air (Fig. 1). There 

 should not be any rooms placed over the stable if this 

 can possibly be avoided. The building blocks should 

 not be arranged in the form of a square, but if this cannot 

 be effected the interval between blocks should be twice the 

 height of the nearest building. Such a stable only requires 

 the introduction of doors and windows to render it the 

 most effective instrument for natural ventilation. 



The process of Diffusion is not a very active one in 

 ventilation. Air may pass through a brick wall, but not 

 if that wall be plastered or whitewashed within. Under 



* These matters will receive attention elsewhere, they are only 

 introduced here as bearing on cubic and superficial space and 

 ventUation. 



Digitized by Microsoft® 



