The Surprising Source of Catgut. How an Animal’s Innards Became a Musical Staple

Introduction

Catgut is a type of natural cord made from the cleaned and purified intestines of sheep, cows, goats, and occasionally other animals. It has been used for centuries in a variety of applications, most notably as surgical sutures. The word “catgut” likely has its origins in the use of cat intestines for stringing musical instruments such as harps in the Middle Ages.

Catgut’s unique properties, including strength, flexibility, smoothness, and biodegradability, make it well-suited for use as surgical sutures. Its ability to be absorbed by the body’s tissues also means that catgut does not need to be physically removed after surgery. Catgut sutures have been utilized since at least 100 AD and became increasingly popular from the 17th century onwards. However, catgut has been largely replaced by synthetic sutures since the mid-20th century.

While no longer commonly used for stitches, catgut continues to have applications in tennis racquet strings, musical instruments, and other specialized uses. Both the manufacturing process and source animals have evolved over catgut’s long history, though sheep intestines remain the most common source.

Etymology

The term “catgut” has an uncertain etymology. According to the Oxford English Dictionary, the earliest known use of the term dates back to around 1550. One theory is that it derives from the use of catgut chordae (string) on a type of ancient Roman lyre called a cithara, which was made with a wooden frame strung with gut strings. The Latin name for this instrument was “cithara” or “citera”, which may have ultimately led to the name catgut.

Another possible origin comes from the Italian word “catena”, meaning chain or string. This term may have evolved into “catgut” in English as a description of the intestines used to make the strings. There are also unconfirmed theories that it refers to the use of actual cat intestines to make the strings.

While the exact roots are uncertain, the term catgut has long been used to describe the tough cords made from animal intestines and used for strings on musical instruments like violins, guitars, harps and tennis racquets up through the 20th century. Despite the name, catgut was rarely if ever made from actual cat intestines, but rather sheep, goat, cow or horse gut.

Manufacturing Process

Catgut is made from the intestines of animals, most commonly sheep, cows, and goats. The intestines are cleaned, twisted, and stretched in a process called catgut manufacture. According to ScienceDirect, the intestines go through a curing process using chromium salts, which gives catgut sutures their durability and slow absorption properties. The curing process can take several weeks, as the intestines are stretched and twisted repeatedly before being cut into strands. Once the catgut strings are cured and dried, they can then be packaged and sterilized for surgical use.

Catgut has traditionally been made by hand in a labor-intensive process. The animal intestines are cleaned, scraped, and then twisted and rolled around small sticks while being stretched and dried. According to Forbes, a cow intestine can produce a catgut string up to 160 feet long through this extensive stretching and twisting. The strings are bundled together and undergo further processing and sterilization before being used as surgical sutures.

Animal Sources

Catgut is made from the intestines of various animals, most commonly from sheep, cows, goats, and horses. Despite the name “catgut”, it is rarely if ever made from actual cat intestines.[1]

Sheep Intestines

The most common source of catgut is sheep intestines. Sheep intestines have an ideal balance of strength, thinness, and elasticity that makes them well-suited for manufacturing surgical sutures and musical instrument strings. The best sheep intestines are taken from young lambs less than one year old. [2]

Cow Intestines


Although less common than sheep intestines, the intestines from cows are another major source material for catgut. Cow intestines are thicker and coarser than sheep intestines. However, they are valued for certain applications where extra thickness and durability is required.

Goat Intestines

Goat intestines provide a source of catgut that is finer than sheep but coarser than cows. Goat catgut offers a middle ground in terms of thickness and strength between the other common animal sources. It is often used for delicate surgical procedures where an extra fine suture is needed.

Sheep Intestines

The main animal source historically used to produce catgut suture has been sheep intestines. Specifically, the submucosal layer of ovine intestines is used to manufacture catgut suture material (https://www.linkedin.com/pulse/manufactured-from-beef-sheep-intestines-catgut-suture-runte-medical). Sheep intestines contain collagen fibers that can be processed into strings or cords for use as surgical sutures. The intestines go through extensive cleaning, scraping, and stretching processes to extract the submucosal layer and produce smooth, strong catgut threads. Sheep intestines have been considered optimal for manufacturing surgical catgut because of their strength, smoothness, and flexibility once processed.

Traditional catgut suture made from sheep intestines is available in a range of sizes for different surgical needs. Chromic catgut sheep suture has been treated with chromic salt solution to increase absorption time and prolong strength retention compared to plain gut sutures (https://iqoniq-medical.com/product/unigut/). While synthetic alternatives have grown in popularity, sheep intestines remain a common source for natural catgut sutures requiring absorption by the body over time.

Cow Intestines

Catgut was historically made from cow intestines. The intestines were cleaned, scraped, and stretched in order to create long, thin strings that could be used as sutures. According to the Wikipedia article on surgical sutures, “The gut suture was similar to that of strings for violins, guitars, and tennis racquets and it involved harvesting sheep or cow intestines.”1 The intestines of cows were commonly used because they provided longer strands that were more durable for suturing than other animals.

The process of actually creating the catgut suture from a cow intestine involved gently scraping away the exterior muscular layers and then twisting or braiding the remaining submucosa layer into a string. The strings needed to be extremely fine, smooth, and strong in order to work for suturing. After processing, the catgut strings were often stored in alcohol or another preservative solution.

While catgut has been replaced by synthetic alternatives in most modern procedures, cow intestines provided the source material for catgut sutures for many decades. The smoothly braided strings created durable, absorbable sutures that worked well for closing and binding wounds until they naturally dissolved.

Goat Intestines

Goat intestines have traditionally been used as a source for manufacturing catgut strings. The intestines are cleaned, twisted, and stretched to create the strings. Goat intestines are valued for their strength and durability which makes them well-suited for catgut manufacturing (See here for additional information on goat intestines used for catgut.) The serosa membrane in goat intestines contains collagen fibrils that provide strength to the strings. The intestines go through an extensive cleaning and processing to create the polished catgut strings.

Other Animals

While sheep, cows, and goats are the most common sources of catgut, other animals have also been used to produce this material. Some less common sources include:

  • Horses – Horse intestines were one of the original sources of catgut. However, horse gut is less common today due to having more elasticity and being more prone to stretching than other types of catgut.[1]
  • Pigs – Pig intestines can be made into catgut, though this material tends to be thicker and stiffer than other sources. It was sometimes used for tennis racquet strings in the past.[2]
  • Deer – Deer intestines have occasionally been used as a source of catgut sutures and strings. However, deer gut is not as strong or smooth as other sources.
  • Kangaroos – In Australia, there were some historical attempts to use kangaroo intestines as a local source of catgut material. However, kangaroo gut never became common.

Overall, while other animals can produce catgut, sheep, cows, and goats remain the standard sources used by modern manufacturers.

[1] Encyclopedia Britannica. “Catgut.” https://www.britannica.com/technology/catgut
[2] Davis, Richard. “The History of Tennis Racquet Strings.” Racquet Research, 5 Jan. 2022. https://www.racquetresearch.com/the-history-of-tennis-racquet-strings/

Modern Alternatives

Catgut has largely been replaced by synthetic materials like nylon, polyester, and polypropylene for use as surgical sutures. These synthetic alternatives have a more predictable absorption rate and cause less tissue reaction compared to catgut sutures (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4164456/).

Common synthetic suture materials include:

  • Polyglycolic acid (Dexon) – Absorbed within 60-90 days
  • Polyglactin (Vicryl) – Absorbed within 60-90 days
  • Polydioxanone (PDS) – Absorbed within 180-210 days
  • Polypropylene (Prolene) – Non-absorbable

Studies have shown that synthetic absorbable sutures like polyglycolic acid and polyglactin provide comparable or better outcomes compared to catgut for procedures like episiotomies and surgeries (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7489783/). The transition to synthetics has allowed for more predictable absorption rates and less tissue inflammation.

## Conclusion

In summary, catgut is a type of cord that has historically been used to make musical instrument strings, tennis racket strings, and surgical sutures. Despite its name, catgut does not actually come from cats. The term refers to cord made from the intestines of grazing animals like sheep, cows, and goats.

To manufacture catgut, workers take intestines from freshly slaughtered animals, clean them thoroughly, scrape off the fat and outer membrane, and steep the intestines in water. Then they twist the intestines to form cords, polish them, and sometimes treat them with antiseptics. The highest quality catgut has traditionally come from Italy.

While catgut was once vital for strings, today most musical strings are made from metal or synthetic materials instead. However, some musicians still prefer the sound quality of real catgut. The material has also been widely replaced by absorbable synthetic sutures in surgery. However, catgut sutures are still used in some circumstances since they provoke less tissue reaction.

In summary, while catgut was once an indispensable material across fields like music and medicine, today it has been largely supplanted by modern synthetic alternatives. However, natural catgut maintains a small niche in select applications where some prefer its unique properties and qualities.

Scroll to Top