92 



MODERN HORSE MANAGEMENT 



[CHAP. 



man of average size it is about 625 square feet. 

 In a horse this is many times greater. A 

 common view held is that a lung at each expira- 

 tion empties itself of air ; this is far from being 

 the case. 



Every time the lung draws in air, by the 

 chest being expanded and the diaphragm being 

 contracted, the little air sacs become larger ; this 

 expansion of the lungs causes the air sac to 

 expand only one-seventh of its original volume. 

 Now, only one-fifth of the air is oxygen, so each 

 time an air sac becomes expanded it receives 

 only one-thirty-fifth of its volume of pure oxygen. 

 The venous blood, when it reaches the lungs, 

 besides receiving a fresh supply of oxygen, gives 

 up a quantity of carbon dioxide, which is a waste 

 product from the cells of the body. 



The air in the lungs, as it is expelled by an 

 expiration, takes this carbon dioxide (C0 2 ) with 

 it, so that the air has a double function : that 

 of taking oxygen to the blood, and that of taking 

 carbon dioxide away from the blood. As the 

 lungs only open and close, approximately, one- 

 seventh of their volume, the air in them must 

 always contain a certain amount of carbon 

 dioxide. 



362. It will also be clear how important it is 

 that the air which is drawn in is as pure as 

 possible, and that which is blown out is taken 

 away from the nostrils as rapidly as possible. 

 In short, unless fresh air is continually being 

 supplied to the nostrils of a horse, his health 

 must be seriously impaired. Also, the oxygen 

 in a closed stable will rapidly become used up, 

 and the stable will soon become filled with a 

 high percentage of carbon dioxide. Air contain- 

 ing as little as \ per cent, carbon dioxide is 

 exceedingly bad for horses to breathe. As long 

 as this impure air remains in a closed stable it 

 will remain impure, but when impure air is 

 allowed to escape into the open air Nature 

 rapidly removes its impurities and transforms 

 it into pure air. This process of changing carbon 

 dioxide back to carbon and oxygen is carried out 

 by plants, i.e. the vegetable kingdom. 



It would, therefore, be possible, if a perfect 

 inflow of pure air and exit of used air were 

 maintained, to keep a horse in a very small 

 enclosed space ; but for various obvious reasons, 

 and also because a certain space must be allowed 

 to avoid a draught, the cubic capacity for a horse 

 must be comparatively large. Experiments have 

 shown that the cubic space in a stable for each 

 horse should be 1,500 cubic feet. Thus, if a 

 stable is 12 ft. high and about 6 ft. wide, it will 

 have to be 21 ft. from the front of the stalls to 

 the back of the stable, or the centre of the 

 passage, if there is a double row of horses. The 

 width of 6 ft., of course, is the width of the 

 stall. It is quite obvious that there are many 

 stables that have not this required air space. 



363. Having got this space for every horse, it 



is necessary that the air in this space be entirely 

 changed every twenty minutes. The large 

 volume of air which enters a horse's lungs at 

 every inspiration, and which comes out impure 

 at each expiration, rapidly causes the 1,500 cubic 

 feet of air to become contaminated. Careful 

 experiments have shown that if there is a large 

 enough inlet and a large enough outlet to allow 

 this space to be refilled every twenty minutes, 

 the horse will obtain all the fresh air that he 

 could possibly require while standing in the 

 stable, if he is not suffering from lung disease. 



Nature assists us to replace the foul air in a 

 wonderful way. Foul air, when it comes out of 

 the lungs, is warm. All gases expand when they 

 are heated. Thus, the same weight of a gas 

 when heated occupies a larger space. That is, 

 a cubic foot of expanded air would weigh less 

 than a cubic foot of cold air. Hence the heated 

 air, being lighter, rises above the heavier cold 

 air. Carbon dioxide (22) normally weighs more 

 than air (14'43), but when heated and mixed 

 with air it weighs less than pure air ; thus the 

 impure air from the horse's lungs rises to the 

 ceiling. If this air cannot continue to rise, but 

 comes in contact with a cold ceiling, it will 

 remain there until it cools down and once more 

 becomes lighter than air, when it will again fall 

 and reach the horse's lungs. Therefore, the air 

 in a closed stable would be breathed over and 

 over again, each time becoming more foul and 

 causing more harm. Thousands of horses in 

 large cities are daily having their health im- 

 paired by bad, and in many eases disgraceful, 

 ventilation. 



364. On the other hand, if this warm foul air 

 is able to rise up and pass through the ventilator 

 in the roof, it escapes into the outside air. So 

 much for the outlet. The most important ques- 

 tion is the inlet of fresh air. This must be 

 nearly as abundant as the outlet. If it is not, 

 the fresh air will get in under the door and 

 through other places, and cause objectionable 

 draughts. If we close up windows and venti- 

 lators we create draughts, as some air will get 

 in some way or other. 



If the inlet is at a suitable height above the 

 ground, and is large, there will be very few 

 draughts along the floor. When the foul air 

 leaves the stable through the ventilator, other 

 air must replace it, or else a partial vacuum 

 will be created in the stable ; and, as Nature 

 abhors a vacuum, the air has, as we said before, 

 to get in somehow. 



365. Windows as the Air Inlet. The best 

 entrance for the fresh air is through a small 

 window about 8 ft. from the ground in front 

 of each horse. The window should be 2 ft. 

 square, hinged at the bottom on the inside wall, 

 to open towards the inside of the stable to an 

 angle of 45. A little plug should be arranged 

 to fit into the window to keep it right open 



