INTRODUCTION. 19 



these. Thus a dihite alkali given before 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 

 sodae, 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 tlie 

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

 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 mercury. 



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 w^hich 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. 



