The commercial catgut suture material is obtained from the small intestine of sheep. The intestines of freshly killed sheep are cleaned of their contents and are placed in cold storage or packaged in brine for transportation. The first 75 meters of the gut is chosen for the preparation of surgical catgut. The intestines are inspected for abnormalities and only suitable gut is chosen for further processing. The intestines or casings are cleaned thoroughly in water.

Removal of Unwanted Layers

The mucous, submucous and serous layers should be separated from the connective tissue. It can be done by placing the cleaned gut in a tub of cold water and allowing it to decompose, by which the gut splits into ribbons. The unwanted tissues can then be removed by scrapping with a blunt knife until only the connective tissue is left intact.

Another method is to split the intestine into two portions by means of a round blunt pointed piece of wood having razor-like blades attached to its periphery. The gut is drawn over the instrument. The intestine is split into a rough and smooth ribbon corresponding to the mesenteric and antimesentric parts of the intestine. The split gut is placed in a tub containing 1% solution of sodium bicarbonate. It is then taken and scraped by means of a machine consisting of a set of rollers, which draws the gut between a smooth cylinder below and a rapidly revolving paddle wheel above, the latter revolving in an opposite direction to the movement of the gut. The ends of the blades of the paddle wheel are provided with flexible leather flappers that beat and scrape the uppermost side of the gut. Then, the gut goes from the scraping machine into fresh sodium bicarbonate solution. This process of scraping and soaking in the sodium solution is repeated six or eight times until both sides of the gut are cleaned of everything but the submucous connective tissue. It is then bleached and disinfected by being placed in a solution of hydrogen peroxide one-third to water two-thirds, to which has been added sufficient sodium bicarbonate to render it neutral. The solution is heated to 900°F and is kept at this temperature for six hours, after which the gut is ready for twisting. When prepared in this way, the gut is free from muscle and mucous membrane or peritoneum.

This process arranges the gut fibers in a parallel way, thus greatly increasing their tensile strength.