One of the more fiendish looking medical instruments ever to come from man's imagination, the scarificator was used for bloodletting. The name certainly does nothing to suggest that it's anything but fiendish, either. There are very few innocuous things in this world that have the word "scar" embedded in their name.
Most popular in the 18th and early 19th centuries, a typical scarificator was rectangular or octagonal in shape and made mostly of brass. Many of them, particularly the European models, were highly decorated with precious little engravings of flowers and leaves and all sorts of other darling little things.
Which, I suppose, is meant to distract the patient from what's inside that pretty polished brass housing -- namely, anywhere between 4 and 20 fierce blades, loaded behind a spring. The doctor or whoever else was doing the bloodletting would place one flat end of the scarificator flush against the skin, pull a little lever on the side or bottom, and with a lovely sound of steel springs coming uncoiled and slapping even more steel, out come the blades. At this point, the instrument is removed from the skin -- go ahead, imagine 20 blades being pulled out of your skin all at once -- and the patient is permitted to bleed out all of the bad humors. Ta da! All better!
The scarificator went out of fashion as the 19th century progressed and people started to figure out about bacteria, since it turns out it's tough to sanitize a whole bunch of blades that usually stay inside a brass housing, namely because a whole bunch of gore and goo comes out of the skin after the blades are retracted.