This is what I got from Google:
English bluebell (Endymion non-scriptus) is an ornamental bulb plant that is grown outdoors and forced indoors for its early spring flowers. This species was formerly included under the genus Scilla. The plant contains glycosides, which are chemically similar to the cardiac glycoside digitalis. Cattle, a horse, and humans were poisoned after ingesting this plant. Children or family pets should be prevented from chewing the plants (Cooper and Johnson 1984).