That is the abbreviation for the suffix -us (or sometimes -os and -is as well, which one it is is determined by context). A person versed in Latin would have no difficulty understanding which suffix is meant. Scribes used these abbreviations quite often to save space and time. Here's a short introduction to the subject.

Your text has other abbreviations as well, the tilde in mebris and on top of the first i in iplicit(us) points to an omitted m (membris and implicitus).

It is an abbreviation. Spirit(funky S) was short for Spiritus. These were common in later hand copied documents.

There are lots of examples here: https://kuscholarworks.ku.edu/bitstream/handle/1808/1821/47cappelli.pdf

Even in modern times, pharmacists are expected to know the applicable abbreviations. 'c' with a bar over it is cum, 's' with a bar over it is sine.

This looks like early-modern printed typesetting and not medieval hand written paleography. Can you provide some context? Book title and author, date, etc.