Well, the use of nitrates and nitrites to cure meat (like the Morton quick-cure stuff) is fairly recent. Historically, sausage recipes used spices, salt, a high fat content, and drying or smoking to preserve the encased meat. Old World sausages are not a lot different than American Indian pemmican in a lot of respects. Pemmican is pulverized meat, deer or bear tallow, and some dried berries packed in hide bags. That stuff was reported to have lasted years in caches used by trappers and explorers.
I was lucky enough to spend some time in Germany as a foolish youth and had sense enough to make a little study of locally made sausages...went along with my appreciation for small town German beer joints.
They all seemed to serve a local sausage they were especially proud of, and I figured with enough beer consumption nothing they came up with would kill me. One that really interested me was sliced liverwurst served in a pickling brine not unlike the brine used here on pickled herring. It was a sweetened, salted vinegar base with onions and peppercorns. I wondered at the time if that was an old way of preserving the more perishable sausage (liverwurst, bloodwurst) without refridgeration. Sure was tasty!