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nerves send branches to tlie bronchial tubes, lungs, heart, stomach, etc. 

 All the orgaus just mentioned may sooner or later become involved in 

 connection with broken wind. It may be said that broken wind is always 

 associated with disorder of the function of digestion. It is claimed that 

 coarse or indigestible food irritates the branches of the pneumogastric 

 nerves which supply the walls of the stomach, and this irritation is re- 

 flected or extended to the branches of the same nerve which supply 

 the lungs, when the lesions constituting broken wind follow. 



In itself broken wind is not a fatal disease, but death is generally 

 caused by an affection closely connected with it. After death, if the 

 organs are examined, the lesions found depend much upon the length 

 of time broken wind has affected the animal. In recent cases very few 

 changes are noticeable, but in animals that have been broken-winded 

 for a long time the changes are well marked. The lungs are paler than 

 natural, and of much less weight in proportion to the volume, as evi- 

 denced by floating them in water. The walls of the small bronchial 

 tubes and the membrane of the larger tubes are thickened. The right 

 side of the heart is enlarged and its cavities dilated. The stomach is 

 enlarged and its walls stretched. And in many old cases the intestinal 

 walls undergo the same changes. The important change found in the 

 lungs is a condition technically called pulmonary emphysema. This 

 is of two varieties: First, what is termed vesicular emphysema, which 

 consists of an enlargement of the capacity of the air-cells (air vesicles) 

 by dilation of their walls ; the walls after a time degenerate, and finally 

 give way, and thus form a communication with other air-cells. The 

 second form is called interlobular emphysema, and follows the first. 

 In this variety the air finds its way into the lung tissue between the 

 air-cells, or, as its name indicates, in the tissue between the small 

 lobules. 



Symjifoms. — Almost every experienced horseman is able to detect 

 "heaves." The peculiar movement of the flanks and abdomen point 

 out the ailment at once. But in recent eases the affected animal does 

 not always exhibit the characteristic breathing unless exerted to a cer- 

 tain extent. The cough which accompanies this disease is peculiar to 

 it. It is difdcult to describe, but the sound is short, and something like 

 a grunt. 



When air is inspired, that is, taken in, it appears to be done in the 

 same manner as in health; it may possibly be done a little quicker than 

 natural, but not enough to attract any notice. It is when the act of 

 expiration (or expelling the air from the lungs) is performed that the 

 great change in the breathing is perceptible. It must now be remem- 

 bered that the lungs have lost much of their power of contracting on 

 account of the degeneration of the walls of the air-cells, and also on 

 account of the paralysis of muscular tissue before mentioned. The air 

 passes into them freely, but the power to expel it is lost to a great 

 extent by the lungs: therefore the abdominal muscles are brought into 

 play. These muscles, especially in the region of the flank, are seen to 



