400 MATERIA MEDIC A AND THERAPEUTICS. 



Carbonic Acid in effervescence, Vegetable Acids and their salts, 

 wines (which are all acid to a degree), and acid fruits and juices, 

 of which Lemon may serve as a type. The familiar effect of 

 acid drinks in relieving thirst cannot, however, be entirely 

 explained by their influence on the nerves of taste. Here the 

 student is introduced to a great physiological law, which we shall 

 frequently have occasion to notice, that acid substances stimulate 

 alkaline secretions, and alkaline substances stimulate acid secretions. 

 The action is probably a local one, the acid or alkali, as the case 

 may be, being quickly absorbed, and reaching the protoplasm 

 of the glands direct. 



Other drugs act as specific sialagogues upon the ter- 

 minations of the portio dura in the salivary glands, or on the 

 cells themselves. Such are Jaborandi, and its active principle 

 Pilocarpin, Tobacco, Physostigma, Mercury and Iodine, and the 

 indirect emetics Antimony and Ipecacuanha. 



Opposed to these measures are the antisialagogues, equally 

 at our service, although but rarely employed. Such are insipid 

 or nauseous articles of food or medicine, with which may be 

 classed depressing emotions and other nervous influences ; dilute 

 alkaline or soapy substances acting locally, such as Potash, Soda, 

 and Lime ; and certain articles of the first importance in the 

 materia medica which act upon the secreting nerves, and may, 

 therefore, be called specific antisialagogues. The type of these 

 is Belladonna (Atropia), with Hyoscyamus, and Stramonium 

 (Hyoscyamia). Tobacco in excess has the same effect, as well 

 as Opium. 



If the natural secretion fail, certain substitutes for the mucus 

 may be employed, which are called demulcents (demulcere, to 

 soothe), as they sheathe the mouth, tongue, and fauces with a 

 protective coating. Such are simple drinks, especially tepid 

 water, toast- water, water and milk; mucilaginous prepara- 

 tions, in a fluid or solid form, including barley-water, gruel, 

 and linseed tea ; various preparations of gelatine and isinglass ; 

 lozenges made with gums ; preparations of starch, eggs, honey, 

 figs, and bread ; palatable oils ; syrups ; and ice. 



4. The excretions of the mouth can also be influenced by 

 means of substances which are thrown out of the system by this 

 channel, such as Iodine, Lead, and Mercury. The therapeutist 

 can hardly be said to avail himself of this means of acting on 

 the mouth. 



5. The mastication and insalivation of the food can also be 

 regulated, on the one hand by insuring time and care in the 

 process of eating, and on the other hand by ordering such a 

 diet as is entirely fluid, or may be thoroughly triturated and 

 exposed to the juices of the mouth. 



