What is the purpose of using the string to tie the forelegs and hind legs during dissection?

To holds the legs apart without rupturing any vein

Explanation:

The purpose of using string to tie the forelegs and hind legs during dissection is to hold the legs apart without rupturing ant vein or artillery for easy dissection procedure (the dismembering of the body of a deceased animal or plant to study its anatomical structure)

when tieing the forelegs and the hind legs the same string is used to tie them and the string is then passed/looped under the dissecting table/tray this way the legs will be held apart and the dissection can commence.