[L. indicum, from India."] A well-known and beautiful blue vegetable dye, obtained from the leaves of several species of plants which grow in the East and West Indies, India, Ceylon, Mexico, Brazil, Egypt, etc. Indigo is very extensively employed in dyeing and calico-printing. White indigo, discovered by Chevreul, results from the action of hydrogen on indigo. Indigo is made artificially in great quantities from cinnamic acid and isatin, which are derived from benzine.

Influen'za, An epidemic disease which comes suddenly, produces severe catarrh, and is very apt to develop into pneumonia or serious affections of other parts of the body. In France it is known as la grippe, which name has become common, and many occurrences of it are upon record, one of the most persistent of which appeared in Europe and the United States in the winter of 1889-90, and was still active more than ten years later. The disease is believed to be of bacterial origin, and is often fatal.