278 MATER i A MEDIC A AND THERAPEUTICS. 



Characters. Rhizome from one to three inches long, and 

 two or three lines thick, cylindrical, contorted, rough from the 

 scars of the coriaceous leaves, and furnished with numerous 

 long slender fibres ; has a peppery taste and peculiar odour. 



Composition. The pharmacology of arnica is still obscure. 

 It contains a small quantity of volatile oil, of complex com- 

 position, and said to yield trimethylamin ; tannic acid ; and a 

 bitter substance, arnicin. 



Preparation. 

 Tinctura Arnica. 1 in 20. Lose, 1 to 2 fl.dr. 



ACTION AND USES. 

 1. IMMEDIATE LOCAL ACTION AND USES. 



Externally. Arnica, applied to the skin, sometimes causes 

 hyperaemia, eczema, and even spreading erysipelas. It would, 

 therefore, appear to increase the activity of the circulation in 

 the skin ; and the tincture in water is a popular application to 

 bruises, preventing swelling, and hastening the absorption of 

 effused blood. It must be used with caution. 



Internally. Arnica is a stimulant to the alimentary canal, 

 like volatile oils in general ; in over-doses a powerful irritant, 

 causing vomiting, pain, and purging, with consequent constitu- 

 tional effects. Probably by reflex action from the stomach 

 (see Caryophyllum, page 242) it stimulates the heart and circu- 

 lation, the brain and spinal cord, in moderate doses ; the pulse 

 being strengthened, and symptoms of nervous debility removed. 

 Arnica has, therefore, been used with success in low forms of 

 fever, delirium tremens, and mental disorder. 



2. ACTION ON THE BLOOD, AND SPECIFIC ACTION AND USES. 



The active principles of arnica enter the blood and thence 

 the tissues, where its effects somewhat resemble those of tur- 

 pentine. If the dose be considerable, the reflex stimulant effect 

 from the stomach is overcome by its depressing action on the 

 circulation and nerve centres ; headache, unconsciousness, and 

 convulsions being induced, and the body temperature lowered. 

 Arnica has thus been employed as an antipyretic, especially in 

 acute rheumatism, but cannot be said to be used now. 



3. REMOTE LOCAL ACTION AND USES. 



Like its allies, arnica is a remote stimulant of the kidneys 

 and skin, and has been given in some cutaneous diseases such 

 as eczema, and in chronic rheumatism. 



