Toilet drain pipe running sideways?

I am helping my brother with his bathroom remodel. It is a 100+ year old house that has been updated at various times over the years. When we took up the subfloor near the toilet, I noticed that the drain pipe from the toilet runs sideways, or even a slight reverse slope for a little bit (less than a foot) before it ties into the stack. The toilet has always worked fine, but I'm wondering how this could possibly work? Is it just that the volume of water coming from the toilet washes through the sideways part and down the stack or what? I guess I'm just worried about putting the floor back down like this.

Ideally you'd have the recommended 1/48 slope (1/4" per foot) in the line. The line is probably a 4" CI (?), so if it's sloped a little bit backward, then you'll have a little bit of a puddle left at the lower end when things settle down after a flush, but not likely any waste to speak of. If it's "always worked" I wouldn't bother fixing it. A real plumbing pro might have a different opinion.

Ha. My toilet drain pipe goes "sideways" for over 20 feet before leaving the house.

Horizontal is fine if it has some slope to it. The larger the pipe, the less it needs.

pipe

The pipe could come frontwards for all the toilet cares. All it wants is a hole in the floor to sit on top of. Once the waste is in the pipe the toilet's job is done.