300 MATERIA MEDIC A AND THERAPEUTICS. 



Characters. Colourless, or white acicular crystals. Sparingly 

 soluble in water, more freely in alcohol and ether. Readily 

 decomposed in solution. Alkaline, readily forming crystallisable 

 salts with acids. It can be chemically resolved into tropin 

 and tropic acid ; and reconstructed by the synthesis of these 

 bodies. One of the products of tropin, called homatropin, has 

 been used as a mydriatic instead of atropia. The intimate 

 cause of the isomerism but non-identity of atropia with the 

 other alkaloids of the atropacese has yet to be discovered. 



Incompatibles. Caustic alkalies decompose it; e.g. Liquor 



Potassse (often prescribed with belladonna) renders it inert. 



Opium, physostigma, and strychnia are in various respects and 



degrees physiological antagonists. See Opium, pages 192 to 197. 



Preparations. 



a. Liquor Atropise. 4 gr. to 1 fl.oz. of "Water and Spirit. Not 



given internally. . 



b. Unsruentum Atropiss, 8 gr. in 1 oz. 



From Atropia is made : 



Atropise Sulphas. Sulphate of Atropia. Source. Made by 

 dissolving Atropia in Diluted Sulphuric Acid and Water, 

 and evaporating. Characters. A colourless powder, 

 very soluble in water and in spirit ; neutral. Dose, T | 7 

 to ^ gr., but not given internally as such. 



From Atropice Sulphas is prepared : 



a. Liquor AtropiaB Sulphatis. 4 gr. to 1 fl.oz. of Distilled 

 Water. Dose, 1 to 2 min., by the mouth ; or 2 to 5 min. 

 of a mixture of equal parts of the Liquor and distilled 

 water, hypodermically. 



ACTION AND USES. 

 1. IMMEDIATE LOCAL ACTION AND USES. 



Externally. Belladonna and atropia, as such or in aqueous 

 suspension or solution, are not absorbed by the unbroken skin, but 

 alcohol, chloroform, camphor, and glycerine, with which they 

 are generally combined, readily convey the atropia through the 

 epidermis. Exposed mucous membranes and inflamed areas of 

 skin still more readily absorb atropia. 



Belladonna depresses the sensory nerve endings, thus acting 

 as a local anaesthetic and anodyne ; the blood-vessels are first 

 somewhat contracted, and then relaxed ; and the motor nerve 

 filaments to underlying muscles reduced in activity. Any other 

 special nerve endings, with which the atropia may come in 



