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Figure 12.—Lavishly decorated scarificator, 18th century. (Held by the Wellcome Institute of the History of Medicine, London. Photo courtesy of the Wellcome.)

The later models (mid- to late nineteenth century) were wider and plainer and had arched or crescent shaped blades (which made a cleaner lesion), but the internal mechanism remained the same. Square scarificators all had 16 steel blades that cut in the same direction and were arranged on three rods of five, six, and five blades respectively. At one end of each rod was a gear pinion. The cocking lever, protruding through an aperture at the top of the scarificator, broadened out into a flat plate with as many gear sectors as blade rods. The plate was held against the interior of the scarificator by a heavy support rod running the width of the scarificator, in such a way that the gear sectors of the cocking lever meshed with the pinions on the blade rods. Pulling up on the cocking lever turned the blades 180 degrees. A heavy flat cantilever spring, attached at one end to the bottom of the case, was caught under a protuberance on the cocking lever and bent as the cocking lever was pulled. 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].)

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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.