DIABETES INSIPIDUS is a morbid condition character ized by the passage of excessive amounts of urine of very low specific gravity (1.002-1•005) . The urine contains no abnormal constituent. The patient has intense and constant thirst and sometimes health appears to suffer very slightly, for the disease runs a slow course. Nevertheless, its debilitating effects may pre dispose to serious and fatal complications. It may terminate in diabetes mellitus. The polyuria must be distinguished from that due to chronic granular kidney and lardaceous disease (see KID NEY DISEASES) and from that occurring in some cases of hysteria. It is best treated by tonics and generous diet, and a free supply of water to drink should never be withheld. Valerian has been found a useful drug. The cause is unknown.