Monocular compound microscope by Paul Waechter, c. 1890
This microscope was specially designed for the microscopic examination of the presence of Trichina in meat. Trichina (Trichinella spiralis) is a parasitic nematode worm that causes trichinosis, a serious disease in humans and other meat-eating mammals. Free Trichinella were seen for the first time by Zenker in 1860 and Rudolph Virchow (1821-1902) succeeded in inducing various German states to make the testing of pig's meat for trichinosis in abattoirs compulsory (c. 1870).
The horseshoe foot has a compass joint to allow the pillar to be inclined. Rising from the compass joint is a tapered cylindrical brass pillar that supports the stage and the rest of the instrument. The substage plano-concave mirror is 32 mm in diameter. Mounted the brass pillar is a rectangular stage, which is mechanically attached to the pillar by means a semicircular collar held with two screws and a central pin projecting forward from the pillar. The brass pillar rises above the stage terminating in round plate fixed with a single screw that holds the limb of the microscope to the pillar. On the leading edge of the limb is a rack and pinion system that controls the movement of the body tube. At the back of the limb is a pinion gearbox equipped with a single milled head on the right side of the microscope, used to focus the body tube. There is no fine focus mechanism, probably due to the fact that magnifications needed for meat inspection are low.
The stage has a recessed central aperture that is designed to accommodate a small blue filter (not included). There is a built-in 5 mm diameter aperture stop on the underside of this aperture. The front part of the stage also has a 15 mm diameter linear slot cut into it to facilitate the forward and back movement of the dovetail mounted glass plate compressorium. Mounted atop the stage is a circular dual glass plate compressorium. The compressorium consists of two glass plates each 7 mm thick. The compressorium is used to squeeze meat samples between the two glass plates, thereby making the meat samples transparent in thin section. A single brass thumbscrew is provided at the center to facilitate the compression of the meat samples and to hold the compressorium to the stage. After the meat specimens are compressed, the thumbscrew can be relaxed slightly so that the glass plates can be rotated freely by hand. The larger diameter glass plate is divided into 4 sectors and each sector is labeled with a number from 1 to 4. The sectors and numbers are etched into this glass plate. Mounted under the stage is a rack and pinion system that allows the observer to move the dovetail bar with the secured glass plates either forward or back for observation of the meat samples in each of the sectors. A milled head that extends laterally from under the right side of the stage controls the forward and back movement. A click-stop mechanism provided under the stage makes the movement is accomplished in precise intervals prevents slippage of the glass plates when the microscope is tilted at an angle to facilitate observations. This very elaborate and cleverly designed setup also allows the observer to manually rotate the compressoium to carefully view the entire compressed meat sample in all 4 sectors.
Paul Waechter (1846-1893) was trained to be an optician and mechanic at the Zeiss Optical Works in Jena. In 1872, Waechter founded his own optical workshop in Berlin. Between the years 1872 and 1892, Waechter produced over 20.000 microscopes, mostly for the examination of trichinae in meat. Waechter obtained the Deutsches Reichs Patent (German Patent) n. 11727 for this instrument on 20 November 1880.