42 GENERAL ACTION OF DRUGS 



(2) BIMINISHING SECRETION. 



Belladonna Stramonium Opium 



Hyoscyamus Acids 



Volatile oils, and drugs containing them, first increase and then decrease 

 bronchial secretion as -a secondary effect. 



(3) ALTERING THE NUTRITION OP BRONCHIAL MUCOUS MEMBRANE. 



Potassium iodide Cod-liver oil Sulphur 



Ammonium chloride 



(4) EXERTING AN ANTISEPTIC ACTION. 



Turpentine Tar Balsam of Tolu 



Terebene Ammoniacum Cubebs 



Terpine hydrate Balsam of Peru Copaiba 



(5) LOCALLY STIMULATING AND ANTISEPTIC TO MUCOUS MEMBRANES. 



Creosote Eucalyptol Guiacol 



Uses. — Expectorants are chiefly prescribed in bronchitis. In the 

 early or dry stage drugs increasing secretion and at the same time de- 

 pressing the circulation are often employed in sthenic cases. These drugs 

 possess less value in the treatment of the horse, on account of comparative 

 insusceptibility to them, than in the case of dogs. 



If exudation is excessive, then drugs lessening secretion are indi- 

 cated. When the disorder is persistent, agents altering and improving 

 the nutrition of the bronchial mucous membrane are beneficial. Bron- 

 chitis accompanied by a copious foul secretion is treated vrith volatile 

 oils, which exert an antiseptic action on the air passages. Expectorants 

 are usually administered with other agents influencing the respiratory 

 tract; e.g., drugs relieving cough and spasm and those stimulating the 

 respiratory movements or circulation. 



Drugs Stimulating the Respiratory Centres.* 



COj is a natural stimulant. 

 Strychnine Cocaine Stramonium 



Atropine Belladonna Ammonium carbonate 



Caffeine Hyoscyamus Strong ammonia 



External counter-irritation and heat. 



Drugs Depressing the Respiratory Centres. 



Morphine, codeine and heroine, chloral and bromides are sedative 

 to the respiratory centre and thus useful in cough, asthma and dyspnea. 



Uses. — Drugs stimulating the respiratory centre and movements are 

 of great value in diseases of the chest — especially pneumonia and bron- 

 chitis — attended with obstruction in the air passages and cyanosis. They 

 promote coughing and efforts at expulsion of secretion and facilitate the 

 entrance of oxygen into the blood. Some, possibly ammonia, stimulate 

 the movements of the ciliae lining the tracheal mucous membrane. 



*The plural is sometimes used because, like the vaso-motor, the centres are 

 bilateral in the medulla. 



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