led. As the blades were turned,
a catch slipped over a tooth on the cocking lever, and held the blades in
place. Nineteenth-century octagonal scarificators generally had two
catches, the first exposing the blades, and the second rotating them a
full 180 degrees. Pressure on the release lever pushed the catch off the
tooth on the cocking lever, thereby releasing the lever and allowing the
spring to snap the apparatus back to its original position. Releasing the
spring brought the blades around so quickly that their movement could not
be seen. (Figure 13.)

[Illustration: FIGURE 13.--Interior of square scarificator. (NMHT 152130
[M-4771]; SI photo 76-9111.)]

In the square scarificators, the top and two sides were detachable from
the bottom and the other two sides. Turning the wing-tip nut on the top of
the scarificator lowered, by means of a yoke, the bottom of the
scarificator that was fitted by grooves into the top. By raising and
lowering the bottom, one could regulate the length of blade protruding
beyond the bottom, and hence the depth of cut.

In the 1790s, the octagonal scarificator that was to become the standard
English-American model began to appear in surgical texts. The early
octagonal scarificator, as illustrated in Latta (1795) and Bell (1801),
had sixteen rounded blades arranged as in the square scarificator, an iron
triggering lever similar to that of the square scarificator, a button
release on the side, and a flat key on top for regulating depth of
cut.[117] Early in the nineteenth century the flat keys were replaced by
round screws. Only the bottom or blade cover of the octagonal scarificator
was detachable. In some of the octagonal scarificators, the round screw on
top ran the height of the scarificator and screwed directly into an
internally threaded post inside the blade cover. In other scarificators,
the screw raised and lowered a yoke whose two sides were attached by
additional screws to side projections of the blade cover.

A notable improvement was made in the early nineteenth century when John
Weiss, a London instrument maker, introduced a 12 blade octagonal
scarificator whose blades, arranged on two rods or pinions, were made to
cut in opposite directions. This advance was mentioned by Mapleson in 1813
and adopted by London professional cuppers thereafter. The advantage of
the innovations was that the skin was thereby stretched, and a smoother,
more regular cut could be made. Weiss's Im