"The Horla" by Guy de Maupassant

Published in 1890.

Shower bath: as best I can find, this is taking a cold shower followed afterwards with rubbing the whole body well with coarse flannel? I'm not entirely sure, and it's not an easy topic to research given the banality of the term "shower bath".

bromide of potassium: a salt used in the 19th century as an anti-convulsant and a sedative.

"belonging to the Mornet": I have no idea what 'Mornet' is in this context. If you recognize it, please leave a comment below!

Herrmann Herestauss: I believe this is a fictional personage?

theogony: the genealogy of the gods

Even in 19th century Paris, some businesses had to put iron bars on the windows. What a shame. There never really was any time in the past that was better than the present, eh? Hence the saying: the more things change, the more they stay the same.

To follow along: https://www.gutenberg.org/files/21327/21327-8.txt