DISEASES OF THE HOESE. 137 



as evidenced by floating- thfim in water. The walls of the small bron- 

 chial 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. The important change found in 

 the lungs is a condition technically called pulmonary emph^'sema. This 

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

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

 by dilation of their walls. The second form is called interlobular, or 

 interstitial, emphysema, and follows the first. In this variety the air 

 finds its wa}^ into the lung tissue between tlie air cells or the tissue 

 between the small lobules. 



Sympfoms. — Almost everj^ experienced horseman is able to detect 

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

 the ailment at once. But in recent cases the aflfected animal does not 

 always exhibit the characteristic breathing unless exerted to a certain 

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

 It is diflicult 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 in perceptible. It must be 

 remembered that the lungs have lost much of their elasticity, and, in 

 consequence, of their power of contracting on account of the degener- 

 ation of the walls of the air cells, and also on account of the paralj^sis 

 of nuiscular tissue before mentioned. The air passes into them f reel}', 

 but the power to expel it is lost to a great extent by the lungs; there- 

 fore the abdominal muscles are brought into play. These muscles, 

 especially in the region of the flank, are seen to contract, then pause 

 for a moment, then complete the act of contracting, thus making a 

 double bellows-like movement at each expiration, a sort of jerky motion 

 with every breath. The double expiratorj^ movement may also be 

 detected by allowing the horse to exhale against the face or back of 

 the hand. It wall be observed that the expirator}^ current is not con- 

 tinuous, but is broken into two jets. When the animal is exerted a 

 wheezing noise accompanies the breathing. This noise may be heard 

 to a less extent when the animal is at rest if the ear be applied to the 

 chest. 



As before remarked, indigestion is often present in these cases. 

 The animal ma}" have a depraved appetite, as shown by a desire to eat 

 dirt and soiled bedding, which he often devours in preference to the 

 clean food in the trough, or manger. The stomach is liable to be over- 

 loaded with indigestible food. The abdomen may assume that form 

 called "potbellied." The animal frequently passes wind of a very 

 offensive odor. When first put to work dung is passed frequently; 



