IKTRODUCTION. 19 



these. Thus a dihite alkali given hefore a meal will 

 stimulate the production of the acid gastric juice, 

 and check the secretion of the alkaline pancreatic 

 juice. Antacids are subdivided into two classes: 



Direct Antacids. — These lessen acidity within 

 the stomach — as liquor potassse, lime water, liquor 

 sodse, chalk, carbonates and bicarbonates of K, Na, 

 Li, Mg, and NH^, and aromatic spirit of ammonia. 



Indirect or Remote Antacids. — These become 

 oxidized in the blood, are excreted in the urine as 

 carbonates, and in this way lessen the acidity of the 

 urine; as liquor sodse, lithium citrate, liquor potassae, 

 potassium acetate, citrate, tartrate, and bitartrate, so- 

 dium acetate and citrate, carbonates and bicarbonates 

 of K, Na, Li, Mg, and NH,. 



Emetics are agents which cause vomiting. They 

 are classed as : 



Local Emetics, which act by irritating the end 

 organs of the gastric, oesophageal, or pharyngeal 

 nerves, and by reflex irritation of the vomiting cen- 

 tre — as alum, mustard, salt, and the sulphates of zinc, 

 copper, and mercurj'. 



General or Systemic Emetics, which act by direct 

 irritation of the vomiting centre in the medulla 

 through the medium of the circulation—as ipecac, 

 apomorphine, and tartar emetic. 



Anti-Emetics are agents which prevent and re- 

 lieve vomiting. They are classed as : 



Local Gastric Sedatives, which act upon the end 

 organs of the gastric nerves — as arsenic, bismuth, 

 cocaine, ice, etc. 



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