medicine, such an obturation of the vessels as prevents the circulation of the fluids, whether of the sound and vital, or of the morbid and peccant kind, through them.

Obturator, in anatomy. See Anatomy, Table of the Muscles.

Obtuse, signifies blunt, dull, &c. in opposition to acute or sharp. Thus we say, obtuse angle; obtuse angled triangle, &c.

Obi, or Ob, a river of the Russian empire in Asia, which rises in the desert of Ichinskia, and running north, joins the Irtis near Tobolsk; and, still keeping its name, continues its course north, and falls into a deep bay called Ohkaya, in about 63 degrees of latitude. The exact course of this river was unknown till the country was surveyed by the Russians; who have given us good maps of it and of all Siberia. The Ob forms the boundary between Europe and Asia, and its course is upwards of 2000 miles in length.