MATERIA MEDICA AND THERAPEUTICS. 23 



MEDICINES ACTING ON THE EYES. 



Mydriatics. — Agents which dilate or enlarge the pupil, 

 whether used internally or externally, belladonna, atropia, hyos- 

 cyamus, stramonium, etc. 



They act by paralyzing the ciliary muscle, and are used to 

 allay irritation, inflammation and pain, also to prevent adhesions 

 between the iris and lens, and to facilitate examination of the 

 eye, especially for cataract. 



Myotics. — Contract the pupil by stimulating the ciliary mus- 

 cle, as calabar bean, and its alkaloid physostigmine, also opium, 

 muscarine, etc. They are used alternately with mydriatics to 

 discover the presence of adhesions of the iris and break them 

 down when of recent occurrence. 



DRUGS ACTING ON RESPIRATION. 



Are termed errhines, expectorants, pulmonary tonics and 

 sedatives. 



The respiratory nerve center of the group of ganglionic 

 cells controlling respiration, is situated in the medulla, posterior 

 to the vomiting center. 



Errhines or Sternutatories. — When applied to the nostrils 

 cause irritation, sneezing and increased secretion; occasionally 

 used to expel by sneezing, foreign substances lodged in the nos- 

 trils, sinuses or respiratory passages, as powdered tobacco, vera- 

 trum album., ipecac, etc. 



Expectorants. — Are agents which modify the secretion of 

 the mucous membrane of the air passages, and promote its ex- 

 pulsion. 



They are used in catarrhal affections of the air passages ; 

 most of them when given in large doses cause vomiting, in those 

 animals that can vomit, and a notable depression of the general 

 circulation. 



They are divided into nauseating and stimulating expecto- 

 rants. 



Lobelia, Ipecac, and Jaborandi are Nauseating Expectorants. 

 In small doses they increase osmosis from the inflamed mucous 

 membrane. In large doses they cause vomiting (when possible) 



