ACTION OF '•' LIXCTUS." 563 



liave they, so far as we know, any effect upon them after they 

 have been absorbed into the blood ; and yet one of the com- 

 monest observations is that glutinous and saccharine substances 

 have a very great power to allay cough when applied to the 

 back of the throat, even in cases where we know that inflamma- 

 tion and consequent irritation exist in the respiratory passai^es 

 below the glottis, at a point which the mucilaginous substances 

 cannot reach. The probable explanation of this action of such 

 substances as marsh-mallow lozenges, jujubes, consisting of gum 

 and sugar and Spanish liquorice, is that the irritation which 

 occasions the cough exists at the root of the tongue and around 

 the fauces, as well as in the trachea, bronchi, or lungs, the com- 

 bined irritation rendering the cough worse than either the one 

 or the other alone would do ; and, therefore, if we soothe the 

 tongue and fauces we relieve the cough, even though the irrita- 

 tion in the bronchial tubes or lung may remain as before. The 

 power of such substances as those mentioned to relieve cough 

 depends, no doubt, to a great extent either on their covering the 

 inflamed and irritable surface directly with a mucilaginous coat, 

 and thus protecting it from the action of the air or from irrita- 

 tion by other substances passing over it, or by exciting an 

 increased flow of saliva or mucus, which has a similar effect. 

 At the same time, we cannot deny the possibility of their having 

 other actions, though with these we are at present unacquainted. 

 The use of the mucilaginous substances containing opium or 

 other sedatives, which we know under the name of " linctus," is 

 a more compHcated one. In them we have the soothing action 

 of the nmcilaginous compound, combined with the local sedative 

 action of morphia, chloroform, or hydrocyanic acid upon the 

 inflamed or irritable mucous surfaces at the root of tiie tongue 

 and back of the throat, and this renders even their local action 

 more powerful than that of a mucilaginous substance alone. 

 Such drugs as opium, hydrocyanic acid, and chloroform have a 

 certain amount of local action upon the peripheral ends of 

 sensory nerves, and lessen their sensibility to impressions. 

 When they are applied to the ends of the nerves only for a very 

 short time, as they are when we swallow these drugs in a liquid 

 form, their local action is comparatively slight. It is much 



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