120 DISEASES OE THE HOESE. 



alone. Arsenic may be given in the form of Fowler's solution, 1 

 ounce three times daily in the drinking water. An application of 

 mustard applied to the breast is a beneficial adjunct. The diet should 

 be the most nourishing. Avoid bulky food. Linseed mashes, 

 scalded oats, and, if in season, grass and green-blade fodder are the 

 best diet. 



THE LUNGS. 



The lungs are the essential organs of respiration. They consist of 

 two (right and left) spongy masses, comimonly called the "lights," 

 situated entirely within the thoracic cavity. On account of the 

 space taken up by the heart, the left lung is the smaller. Externally, 

 they are completely covered by the pleura. The structure of the lung 

 consists of a light, soft, but very strong and remarkably elastic tissue, 

 which can only be torn with difficulty. Each lung is divided into a 

 certain number of lobes, which are subdivided into numberless 

 lobules (little lobes). A little bronchial tube terminates in every 

 one of these lobules. The little tube then divides into minute 

 branches which open into the air cells (pulmonary vesicles) of the 

 lungs. The air cells are little sacs having a diameter varying from 

 one-seventieth to one two-hundredth of an inch; they have but one 

 opening, the communication with the branches of the little bronchial 

 tubes. Small blood vessels ramify in the walls of the air cells. The 

 air cells are the consummation of the intricate structures forming 

 the respiratory apparatus. They are of prime importance, all the 

 rest being complementary. It is here that the exchange of gases takes 

 place. As before stated, the walls of the cells are very thin ; so, also, 

 are the walls of the blood vessels. Through these walls escapes from 

 the blood the carbonic acid gas that has been absorbed by the blood 

 in its circulation through the different parts of the body ; and through 

 these walls is absorbed by the blood, from the air in the air cells, the 

 oxygen gas which is the life-giving element of the atmosphere. 



CONGESTION OF THE LUNGS. 



Congestion is essentially an excess of blood in the vessels of the 

 parts affected. Congestion of the lungs in the horse, when it exists 

 as an independent affection, is generally caused by overexertion when 

 the animal is not in a fit condition to undergo more than moderate 

 exercise. Very often what is recognized as congestion of the lungs 

 is but a symptom of exhaustion or dilatation of the heart. 



The methods practiced by the trainers of running and trotting 

 horses will give an idea of what is termed " putting a horse in condi- 

 tion " to stand severe exertion. The animal at first gets walking 

 exercises, then after some time he is made to go faster and farther 

 each day ; the amount of work is daily increased until the horse is 



