DRUGS ACTING ON THE DIGESTIVE ORGANS 25 



bloody diarrhoea, congestion of the mucous membrane of 

 the alimentary canal and severe colic. They may produce 

 death in poisonous doses with collapse by reason of gastro- 

 enteritis. Drastics greatly increase both peristaltic action 

 and secretion, and are contra-indicated in irritable and in- 

 flamed conditions of the digestive tract. They are, however, 

 indicated for their revulsant or derivative effect (i.e., to dilate 

 the blood vessels in the alimentary canal and to cause an 

 outpouring of serum from thei blood, thus relieving conges- 

 tion in, other parts) in some acute inflammations,, as in brain 

 diseases. Their medicinal action is often attended with 

 considerable and irregular peristaltic contractions, so that 

 griping occurs. The latter is prevented by suitable combi- 

 nation with other purgatives ; with hyoscyamus and bella- 

 donna ; or with carminatives, as ginger. The drastics in- 

 clude : 



Croton oil Scammony 



Colocynth Jalap 



Gamboge Elaterium 



4. Hydragogue Purgatives. — Hydragogues are agents 

 which chiefly increase the fluidity of the intestinal contents. 

 They include : 



(a) SALINE PDRSATIVES 



Magnesium sulphate Sodium phosphate 



Sodium sulphate Potassium bitartrate 



(b) DRASTICS 



Jalap Scammony 



Elaterium 



The salines stimulate secretion by reason of their bit- 

 terness, and by their irritant and specific properties. They, 

 moreover, hold on to the fluid thus secreted and hinder its 

 absorption because of their slow diffasibility. Purgation 

 follows, owing to the mechanical effect of the increased 

 fluidity in the bowels, and since the augmented bulk of the 

 intestinal contents excites peristaltic action. When it is 

 desirable to remove fluid from the blood the salt should be 

 given in concentrated solution, but when a speedy purgative 



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