Iris sphincter muscle Iris sphincter muscle The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil. It is found in vertebrates and some cephalopods. Initially, all the myocytes are of the smooth muscle type but, later in life, most cells are of the striated muscle type. Its dimensions are about 0.75 mm wide by 0.15 mm thick. In humans, it functions to constrict the pupil in bright light (pupillary light
1st Arkansas Light Artillery Battery (Colored) 1st Arkansas Light Artillery Battery (Colored) The 1st Arkansas Light Artillery Battery (African Descent) was a artillery battery that served in the Union Army during the American Civil War. The regiment was composed of African American enlisted men commanded by white officers and was authorized by the Bureau of Colored Troops which was created by the United States War Department on May 22, 1863. The battery was organized at Pine Bluff, Arkansas, on June 4, 1864. Then unit was re-designated as Battery "H", 2nd U.S. Colored Light Artillery on December 13, 1864. Mustered out on August 10, 1865. The battery