THE HORSE~-GENERAL CARE. 219 
taken into these organs. The blood in the veins, on the other hand, is of a 
dark-red color, bearing the impurities taken from all parts of the system. 
By experiment it has been shown that pure oxygen gives this scarlet color 
to the blood, while no other gas does. Hencc, it can only be that it is 
oxygen which purifies the blood. Again, it is found that, if a horse takes 
in one hundred cubic inches of pure air at one breath, he takes about eighty 
cubic inches of oxygen and twenty of nitrogen, these being usually very 
slightly reduced by traces of carbonic gas. But the one hundred cubic inches 
of air thrown from the lungs contains about fifteen of oxygen, eighty of 
nitrogen, four of carbonic gas, and one of water-vapor. Thus the air by 
breathing loses what is best for life, and takes what is harmful. If the 
same air be breathed over time and again, it is clear that it must soon 
utterly fail to sustain life, being indeed very poisonous. 
When it is known that a horse will breathe about fifty thousand cubic 
inches of air in an hour, generating about five thousand cubic inches of car- 
bonic gas, some idea may be gained of the demand for provisions for 
changing the air often in an occupied stable. Many expcriments have been 
made on horses stabled in large numbers, and it has been always shown 
that sickness and death are much less frequent when proper room and ven- 
tilation are afforded. Suitable ventilation consists, first, in the introduction 
of a sufficient quantity of pure air without draught; second, in the removal 
of foul air by other outlets than doors or windows. The first part leads to 
two important questions, namely, what is a sufficient quantity of air for each 
horse, and how is it to be supplied? Each horse requires a space of not less 
than two thousand cubic feet, and the air should be changed at least three 
times an hour. The windows and inlets for fresh air should be placed well 
above the animal, the former so arranged that the wind will not blow 
directly on him. 
As the space necessary for each horse is too large to be practicable for 
most private establishments, we must next consider how we may have 
healthy stables with less space. It is quite possible by attending to the fol- 
lowing rules of ventilation: First, breathed air being lighter than atmos- 
pheric, it ascends toward the roof, passes out if no obstruction is in its way, 
and is replaced by pure air admitted from doors, windows, and other inlets. 
Secon, if carbonic or other gases be confined by ceiled roofs or otherwise, 
they become condensed and diffused, mingling with the pure atmosphere 
and rendering it injurious to health. These rules have no reference to cubic 
space, but simply require a free outlet above for the impure air, and free 
inlet through windows or other openings by which the vacuum can be 
instantly filled. The simplest way of carrying out these rules is to do 
away with ceilings and lofts overhead, and merely have the sides boarded 
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