The tough, dried, twisted string used today in making violin strings, tennis racket strings, strings to thread looms, and thread for surgical stitches is NOT made from a cat’s guts and never has been.
Most catgut is made from the intestines of sheep and hogs. These intestines are cut into long ribbons, then cleaned and dried.
Next they are spun into string and then polished.
Catgut is also used in the mechanisms of clocks and typewriters.