342 PRINCIPLES OF VETERINARY SCIENCE 



tractile power. The disease occurs oftenest in old, hard-worked 

 horses that are greedy feeders. 



Causes. — Bulky foods, indigestible foods, and foods which 

 ferment easily all lead to over-distention of the stomach and 

 to excessive pressure upon the diaphragm and lungs. Dusty 

 fodder, especially hay which has been wet during harvest, or 

 over-ripe hay, is harmful and may induce heaves. There is evi- 

 dence that heaves is inherited or at least a tendency to it is 

 inherited. For example, a Clydesdale mare owned by the Uni- 

 versity of Wisconsin had a pronounced case of heaves and two 

 of her foals developed the disease before they had reached five 

 years of age. 



Symptoms. — A peculiar, dry, droning cough is heard before 

 the difficult breathing, later so characteristic, is noticeable. 

 The cough is explosive in nature and soon becomes very marked; 

 furthermore, it is aggravated by dust and is often accompanied 

 by expulsion of gas from the rectum. Inhalation is normal, 

 but exhalation is labored and difficult. This requires the patient 

 to make a special effort to force out the air. As a result, there 

 occurs a "double-pumping action" of the flanks with two expul- 

 sive efforts instead of one. This produces the so-called "heave- 

 line" seen along the flanks of affected horses. With exercise 

 these symptoms are much intensified. Disguised cases can be 

 detected, or tests can be carried out by feeding all the dusty hay 

 the horse will eat, then giving plenty of water and driving him 

 briskly. 



Treatment. — After the disease is once developed it is impossible 

 to effect a cure for anatomic structures have been destroyed, so 

 treatment can only be palliative. It is said that horses suffering 

 from heaves when taken to an arid country, where the disease 

 is unknown in native horses, become serviceable and seldom are 

 troubled thereafter. By reducing the roughage to a minimum 

 and increasing the concentrates accordingly it is possible to 

 make a badly affected animal serviceable. When grass and roots 

 are available they may be fed in place of hay to good advantage. 

 To relieve heaves nothing has been found so beneficial as arsenic. 

 It is used in the form of Fowler's solution. The remedy may be 

 given in J^-ounce doses three times a day, with a tablespoon of 

 Carlsbad salts on the grain. When continued over a long period, 



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