No. 4.] STABLE MANAGEMENT. 181 



I have entered rather fully into the subject of water, for 

 the reason that I am persuaded we have many diseases 

 affecting horses and cattle, particularly the latter, which arc 

 due to its influence. 



There can be no doubt that for the full enjoyment of 

 health an unlimited and pure supply of water is necessary ; 

 and, though the effects of a bad supply may not produce in 

 many cases any positively prejudicial effect, such as we can 

 see, yet it must be a means of exposing the health of animals 

 to risk, by lowering the tone of the system, and rendering 

 them more susceptible to contract zymotic poisons when 

 these are present. 



Impurities in the Air. 



It is not surprising to find that the impurities found in 

 the air are numerous, and derived from many sources. The 

 importance of these impurities is very great, when we con- 

 sider that, in whatever form they exist, they obtain a 

 direct entry into the animal's body by means of the respira- 

 tory passage. 



The lungs of a horse will contain nearly one and one- 

 half cubic feet of air, and at each respiration about one hun- 

 dred and forty cubic inches are drawn through the trachea ; 

 the surface of the lungs to which this amount of air is 

 exposed is calculated to be equal to two hundred and eighty- 

 nine square feet. Air, then, containing impurities, is ex- 

 posed to an absorbent area within the body equal to five 

 and a half times the surface of the skin. 



Air is rendered impure by the products of respiration and 

 the decomposition of excreta; for convenience of descrip- 

 tion, therefore, the impurities of air are divided into organic, 

 inorganic and gaseous. 



Organic impurities, in small proportions, always exist in 

 the air of places occupied by animals. 



Organic impurities exist in the form of solid particles, 

 accompanied in many cases by gases which are given off 

 from them. These particles, such as bacteria, spores or 

 fungi, are only of microscopical dimensions; others, such 

 as vegetable fibre, epithelial cells, etc., are much larger. 



We know very little about these living particles of matter 



