Catgut is a type of cord that is prepared from the natural fibre found in the walls of animal intestines. Usually sheep or goat intestines are used, but it is occasionally made from the intestines of cattle, hogs, horses, mules, or donkeys..
The word catgut may have been an abbreviation of the word "cattlegut". Alternatively, it may have derived by folk etymology from kitgut or kitstring — the word kit, meaning fiddle, having at some point been confused with the word kit for a young cat.
In order to prepare catgut, the intestines are cleaned, freed from fat, and steeped in water. After that, the external membrane is scraped off with a blunt knife. The intestines are then once again steeped for some time in lye (a caustic alkali, usually potassium hydroxide or sodium hydroxide), and then smoothed and equalized by drawing out. Next, they are subjected to the antiseptic action of the fumes of burning sulfur (i.e. sulfur dioxide), dyed if necessary, sorted into sizes, and twisted together into cords of various numbers of strands according to their uses. The best strings for musical instruments are reputedly from Italy, and are called “Roman strings”. It is found that lean animals yield the toughest gut.
Common uses 
For a long period, catgut was the most common material for the strings of harps, lutes, violins, and violas, as well as other stringed musical instruments, as well as older marching snare drums. Most musical instruments produced today use strings with cores made of other materials, generally steel or synthetic polymer. Gut strings are the natural choice for many classical and baroque string players, and catgut strings are still most commonly preferred in concert-tension pedal/grand and some lever harps because they give a richer, darker sound as well as withstanding high tension within low alto, tenor, and high-bass ranges.
Catgut suture was once a widely used material in surgical settings. There is debate about whether to continue using catgut in a medical setting, since cotton is usually cheaper and wounds closed with either cotton or synthetic threads are less prone to infection. Catgut sutures continue to be used in developing countries where they are locally less expensive and easier to obtain. In addition, catgut is still used as a high-performance string in tennis racquets, although it had more popularity in the past and is being displaced by synthetic strings.
- Underwood, Oscar Wilder (1913). "Tariff schedules: Hearings before the Committee on ways and means". Strings for Musical Instruments. p. 5691. Retrieved February 27, 2010. "[T]here is no such thing as crude catgut or catgut unmanufactured. Catgut is a manufactured article and a finished product; the crude form are the intestines or guts of sheep or other animals." More than one of
- Roenigk, Randall K.; Henry H. Roenigk. Roenigk & Roenigk's dermatologic surgery: principles and practice. p. 93. Retrieved February 2010. "Catgut sutures are derived from the submucosal layer of the small intestine of sheep and the serosal layer of the small intestine of cattle."
- BBC: The unusual uses for animal body parts
- Therapeutic Gazette
- Workshop Companion
- Cotton vs Catgut
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.