GENERAL ACTIONS OF DRUGS. 



Drugs Acting on the Digestive Organs. 



Sialagogues are agents increasing the secretion of saliva. 

 Antisialagogues are agents diminishing salivaiy secretion. 

 Among the sources of saliva — the parotid, sublingual and 

 submaxillary glands — the latter have received most study. 

 The chorda tympani, with its centre in the medulla, is one of 

 the two nerves supplying the submaxillary gland. It con- 

 tains two sets of fibres, the secretory and vasodilator. 

 Hence stimulation of this nerve, or its centre, whether im- 

 mediately or reflexly, leads, by means of its vasodilator 

 fibres, to dilatation of the blood vessels and enhanced vascu- 

 larity of the gland, and so indirectly to greater secretion ; 

 while, through excitation of the secretory fibres, the proto- 

 plasm of the glandular cells is influenced and secretion 

 directly increased. 



Eeflexly the g^and is stimulated by drugs exciting the 

 peripheral terminations of the gustatory (lingual branch of 

 the fifth nerve) and glossopharangeal nerves in the mouth ; 

 the vagus endings in the stomach; by agencies sending 

 pleasurable impressions to the brain through the medium of 

 the eyes or nose ; or by stimulation of other sensory nerves. 

 The submaxillary gland is also supplied by a branch of the 

 cervical sympathetic accompanying the submaxillary arter- 

 ies. Stimulation of this nerve, or its centre, causes vascular 

 constriction in the gland and inhibition of secretion. 



Sialagogues are often classed under three heads. Ist, 

 Specific sialagogues, acting directly on the mechanism con- 

 cerned with secretion, i.e., the gland cells, or nervous appara- 

 tus. Pilocarpine is the best example of the specific class. 

 It stimulates the gland cell or peripheral nerve endings. 

 2nd, Reflex sialagogues, exciting sensory nerve terminations 



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