Foxglove (Digitalis purpurea) Foxglove is a biennial plant that 
is native to England. There are many common names to foxglove.
The Irish call it 'dead man's thimbles' because of the harmful juice
that it secrets. The name foxglove derives from the legend that
bad fairies gave the plant to the fox so it could quiet its footsteps 
with the blossoms while raiding the chicken farms. Willliam 
Withering, botanist and physician, observed that the country 
people of Shropshire used foxglove leaves as a cure for dropsy 
and from this he showed the value of foxglove in treating heart
disease. The active ingredient is the glycoside digitoxin which 
has been isolated and used as digitalis, for congestive heart 
failure and abnormal heart beat. Overdose of the drug causes
colour vision abnormalities (yellow-blue), visual hallucinations,
scotomas, retinal toxicity with abnormal ERG amplitudes.