Typical scarificators consist of 4-12 bladesconstructed so as to be operated by a powerful spring.  The cutting edges of the knives are elliptical in form, and are all designed to cut at the same depth, theextent of which may be regulated by a screw device,  upon coking the lever and deploying the blades, the incisions are madequicklyso as to produce little pain.  The inherent complexity of the instrument and difficulties with cleaning caused it to fall from favor.