16 VETERIN"ARY MATERIA MEDICA. 



noea by decreasing the irritability of the respiratory 

 centre or by decreasing the irritability of the respira- 

 tory nerves — as opium, hydrocyanic acid, cannabis 

 indica, codeine, and amyl nitrite. 



Expectorants are agents which modify the bron- 

 cho-pulmonary mucous secretion and promote its ex- 

 pulsion. They are divided into Nauseating Ex- 

 pectorants and Stimulant Expectorants. 



Nauseating Expectorants in small doses increase 

 osmosis from the inflamed mucous membrane, while 

 large doses cause vomiting and the mechanical ex- 

 pulsion of the mucus. They also increase secretion 

 generally and lower blood pressure — as ipecacuan- 

 ha, lobelia, jaborandi, and the antimonial salts. 



Stimulant Expectorants. — These are eliminated 

 from the system mainly by the bronchial mucous 

 membranes, which they stimulate in this way, alter- 

 ing the secretion and facilitating expulsion. They 

 increase blood pressure and diminish secretion 

 genercdly — as the ammonium salts, squills, senega, 

 the turpentines, and balsams of Peru and tolu. 



Ciliary Excitants promote expulsion of the bron- 

 chial mucus by reflex excitation of the tracheal and 

 bronchial cilia when dissolved in the mouth. This 

 group includes potassium chlorate and the chlorides 

 of ammonium and sodium. 



Agents Acting on the Circulation. 



Cardiac Stimulants are such agents as rapidly 

 increase the force and frequency of the pulse in de- 



