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) was assigned to garrison duty at Pine Bluff, Ark. 7th Army Corps, Dept. of Arkansas, till December, 1864. The battery saw action at Prior Creek on September 18, 1864. The battery was involved in the Expedition to Mount Elba, Ark., and the skirmish at Saline River, January 22-February 4, 1865. Mustered out on August 10, 1865. 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