ACTIONS AND USES 487 



tincture. It occurs in colourless acicular crystals, is volatile, 

 has a bitter taste, is soluble in 300 parts water, readily 

 soluble in alcohol and ether, and in chloroform. The 

 more soluble sulphate, obtained by neutralising atropine 

 with diluted sulphuric acid, is used in preference to the 

 alkaloid. It gives a citron-yellow precipitate with gold 

 perchloride. An alcohol solution of mercuric chloride added 

 to a crystal or strong solution of atropine causes a precipi- 

 tate, which becomes red on standing or when boiled. It 

 powerfully dilates the pupil. 



Atropine can be split up into tropic acid and tropine, 

 and this base, reunited with other acids, forms tropeines. 

 When combined with oxytoluylic acid, the crystalline 

 homatropine is produced, and is used as the soluble hydro- 

 bromide. It is similar to but weaker than atropine, and 

 the solution is preferred by oculists, as its effects, although 

 as promptly and effectually produced, are not so incon- 

 veniently persistent as those of atropine sulphate. Isomeric 

 with atropine is hyoscyamine, whilst hyoscine differs only 

 slightly in its formula. They occur along with atropine in 

 belladonna and other plants of the order Solanaceae. 



ACTIONS AND USES. Belladonna and atropine, combined 

 with glycerin, alcohol or chloroform, which promote pene- 

 tration, and, applied topically, paralyse sensory nerve- 

 endings, and hence relieve irritability and pain. Mainly by 

 paralysing the terminals of the third nerve, they dilate the 

 pupil, and are serviceable in relieving congestion and 

 inflammation of the eye, and in facilitating its examination. 

 Atropine is readily absorbed by mucous surfaces, and exerts 

 its physiological effects on the organs with which it is 

 brought into contact. Toxic doses, after stimulating, 

 paralyse the spinal cord, brain, and medullary centres, 

 causing irregular movements and delirium, with coma from 

 impaired respiration, and kill by asphyxia. Medicinal doses 

 stimulate respiratory and cardiac action, and hence combat 

 collapse, respiratory depression, and poisoning by ptomaines. 

 They antagonise spasm, are used both topically and inter- 

 nally in cases of intestinal and urinary colic and in con- 

 stipation. They diminish the secretion of the salivary, 

 sweat, gastric, mucous, and mammary glands, but not 



