Vaccinator

Patent model for John Zirbes, "Vaccinator," U.S. Patent 131,729 (Sept. 24, 1872). According to Zirbe's patent, he claims to have improved the vaccinator by simplifying its construction, making the case out of a single piece of metal. He used a "spring-ring or annular thumb piece" (the circular finger ring on the back of the device) from which come two "shanks." The shanks to which he refers are the upper and lower halves of the device body - note the seam running horizontally along the casing. The seam between these shanks allows the upper and lower halves to be separated via the trigger-lever, effectively 'cocking' the device open. When the halves snap back together (by force of the annular ring that unites them) the snapping action causes the needle (held by the top half) to snap down and into the socket (which is in the lower half), thus accomplishing the vaccinating action.

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