162 ELEMENTS OF HIPPOLOGY. 



Thick wind is the name for the chronically diseased and 

 thickened condition of the smaller bronchial tubes. The amount 

 of blood that can be purified is limited by this disease, and the 

 horse shows distress and labors when worked fast or hard. He 

 seems to struggle for his wind — to gasp for breath. It is not 

 accompanied by noise, and the inhalations and exhalations recur 

 at equal intervals. There is no medical treatment for this dis- 

 ease. If the horse is very carefully fed, is not exercised at all 

 while his stomach is full, and is worked lightly and at slow 

 gaits, he may finally recover partially, and gradually become 

 more and more serviceable. 



Broken wind or heaves is caused either by a rupture of the 

 air-cells, or by a partial paralysis of the muscles of the cells that 

 assist in expelling the air. In this disease the ordinary action 

 of the lungs and diaphragm is not enough to clear the lungs, 

 and a second contraction is necessary. 



The diaphragm is a dome-shaped muscle, rising from the 

 abdomen into the hollow of the chest. By its muscular action 

 the lungs are squeezed against the ribs and the air thus mechan- 

 ically pushed out of them. With the withdrawal of the dia- 

 phragm the lungs expand and follow it, and so fill themselves 

 with the fresh air that is so necessary to the life of the animal. 

 If the stomach is overloaded with coarse food, the diaphragm 

 will be mechanically and constantly pushed against the lungs, 

 and so limit their powers of expansion. While this condition 

 exists, if the animal is called on for any extra effort, the lungs 

 will not respond to the demands made on them by the circula- 

 tion, and the cell walls will be ruptured in consequence. When 

 the processes of digestion remove the obstruction to the lungs' 

 proper action, the evil will still remain. The lung-cells that 

 have been ruptured will leak air into the lung tissue itself, and 

 this air is expelled with difficulty. Horses living in a dusty or 

 badly- ventilated stable are predisposed to heaves. The lungs, 

 being constantly irritated, become chronically inflamed, and the 



