Digitalis and blue halos around lights), convulsions, and deadly disturbances of the heart. For a case description, see the paper by Lacassie. Vincent van Gogh's "Yellow Period" may have been influenced by digitalis therapy which, at the time, was thought to control seizures. As noted above, other oculotoxic effects of digitalis include generalized blurry vision, as well as seeing a "halo" around each point of light. In some instances, people have confused digitalis with the relatively harmless comfrey ("Symphytum") plant, which is often brewed into a tea, with fatal consequences. Other fatal accidents involve children drinking the water in a vase
Plant physiology plants produce a vast array of chemical compounds with unique properties which they use to cope with their environment. Pigments are used by plants to absorb or detect light, and are extracted by humans for use in dyes. Other plant products may be used for the manufacture of commercially important rubber or biofuel. Perhaps the most celebrated compounds from plants are those with pharmacological activity, such as salicylic acid from which aspirin is made, morphine, and digoxin. Drug companies spend billions of dollars each year researching plant compounds for potential medicinal benefits. Plants require some nutrients, such as carbon and