DRUGS ACTING ON THE RESPIRATORY ORGANS 39 



Uses. — Mydriatics are useful in dilating the pupil for examination 

 of the eye, and to prevent adhesions of the iris in central corneal ulcers ; 

 in keratitis, to overcome photophobia and blepharospasm; and in iritis, 

 to secure rest of the iris and ciliary muscles. 



(2) Myotics 



(a) ACTING LOCALLY. (b) ACTING CENTRALLY. 



Physostigmine Stimulate third Anesthetics 



Pilocarpine nerve endings Opium 



Uses.- — Myotics are employed to prevent prolapse of the iris in 

 wounds and ulcers of the cornea; to antagonize the effect of atropine; to 

 prevent the entrance of light in painful disorders of the eye; to lessen 

 intra-ocular tension in glaucoma* ; and, in alternation with mydriatics, 

 to break up adhesions to the iris. All the local mydriatics and myotics 

 mentioned above act on the ciliary muscle to destroy the power of accom- 

 modation. Intra-ocular tension in glaucoma is usually increased by atro- 

 pine and other mydriatics, but is diminished by eserine and pilocarpine. 



(B) Drugs Acting on the Ear. 



Strychnine makes the hearing (and sight) more acute; while sali- 

 cylic acid, salicylates and quinine cause, in man, subjective symptoms, 

 including fullness, roaring and buzzing noises in the ears. 



DRUGS ACTING ON THE RESPIRATORY ORGANS. 



It is impossible to describe under this head all the drugs influencing 

 the respiratory tract. Thus, agents affecting the circulation exert a 

 powerful action on the blood supply and functions of the respiratory 

 organs. The application of counter-irritants and heat and cold exter- 

 nally, reflexly produce notable alterations of pulmonary conditions. 

 Emetics are indirectly serviceable in assisting the expulsion of exuda- 

 tions from the upper air passages in dogs. Furthermore,. medicines hav- 

 ing a depressing action on the nervous system are of importance in res- 

 piratory disorders in relieving cough and spasm. We shall consider here 

 those agents acting on the respiratory apparatus itself. 



Drugs Acting on the Respiratory Mucous Membrane. 



Errhines, or sternuatories, are drugs which are introduced into the 

 nostrils to cause irritation, coughing and sneezing and expulsion of secre- 

 tions, parasites and foreign bodies from the nasal chambers and upper air 

 passages. They are rarely of any value, and include tobacco, ipecac, 

 euphorbium, ammonia, chlorine and sulphurous anhydride. 



*By opening up the filtration angle at the periphery of the anterior chamber 

 and allowing drainage of lymph through the lymph spaces there into the canal of 

 Schlemm, or to contraction of the intra-ocular vessels, so lessening secretion 

 (Gronholm). 



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