THE AKMY HORSE. 15 



Irregular breathing is that condition where there is a want of 

 harmonious correspondence between the inspiratory and expira- 

 tory movements, and is observed in the disease connnonly 

 known as " broken wind " or " heaves." The inspiratory move- 

 ment in this affection is performed quickly and with jerky 

 effort, while the expiratory movement is performed slowdy and 

 with a double action, more particularly of the abdominal 

 muscles. Irregular breathing often becomes spasmodic or con- 

 vulsive during the progress of the disease. 



The mean temperature of the horse in the internal part 

 which is most easily accessible, the rectum, may be estimated 

 at from 99° to 101° F. In very young animals the temperature 

 is commonly about 101°, but in very old ones it has been known 

 to be as low as 96° F. The temperature of the external parts 

 of the body becomes lower according to their distance from the 

 heart, and liable to much variation from the state of the sur- 

 rounding atmosphere. 



The production of animal heat is due to certain chemical and 

 vital changes which are continually taking place in the body ; 

 these changes consist in the absorption of oxygen by the capil- 

 laries in the lungs, and the combination of that oxygen with 

 the carbon and hydrogen derived (first) from the disintegra- 

 tion of animal tissues and (second) from certain elements of 

 the food which have not been converted into tissue. 



This combination Avith oxygen, or oxidation, not only takes 

 place in the blood, Avhich may be looked upon as a fluid tissue, 

 but in the tissue cells also, in all parts of the body, the animal 

 heat being maintained by the natural changes w^hich are essen- 

 tial to a healthy condition. 



As previously stated, oxygen is absorbed from the air by the 

 capillaries of the lungs in respiration (breathing). Expired 

 air is found to have lost about 10 per cent of the oxygen 

 contained in pure air, and td have accumulated a like amount 

 of a combination of carbon and oxygen, called carbonic acid 

 gas. If we imagine the animal breathing and rebreathing the 

 same air, it can be seen that the oxygen, so necessary for the 

 purification of the blood, would soon diminish to a dangerous 

 degree. Hence, we realize the importance of a large supply of 

 air to draw on and the necessity of good ventilation. At each 

 inspiration the horse draws about 250 cubic inches of air into 

 the lungs, and he therefore requires about 2 cubic feet per 

 minute, or 120 per hour. It is customary, in building ordinary 



