Catgut treated with chromium salts, known as chromic catgut, is also used in surgery. Catgut Chrome (B Braun) suture is a variant treated with chromic acid salts. The original sutures were made from biological materials, such as [[catgut suture]] and [[silk]]. Catgut suture was once a widely used material in surgical settings. Different harps may use strings of catgut, nylon, metal, or some combination. All seams had been sewn with small stitches in catgut. These instruments typically used catgut (animal intestine) and other materials, including silk, for their strings. Strings were first made of sheep's intestines (called "catgut"), stretched, dried and twisted. The strings themselves were originally made of catgut. When Squiggly saved Whopper from Catgut, Whopper and Squiggly are good friends. Strings may be "plain" (consisting only of a single material, like catgut, nylon, or steel). Later lines were constructed from horse hair or silk thread, with catgut leaders. Despite the name, catgut manufacturers do not use cat intestines. Sterile catgut was finally achieved in 1906 with [[iodine]] treatment.