Schmidt’s Microscopic Manipulator (1859)

The Microscopic Manipulator, a screw-operated instrument invented by Dr. H. D. Schmidt of Philadelphia (d. 1889), is regarded as the first micromanipulator. Schmidt’s instrument permitted him to dissect fresh liver tissue under the microscope in order to discern its microscopic structures. At the time, dissections of fresh tissue performed under magnification depended on low-powered lenses and handheld tools.

Schmidt described his Microscopic Manipulator in a long paper published in 1859 in The American Journal of Medical Sciences. He wrote on his histological investigations of the Hepatic lobules of the liver, citing as inspiration the “great discrepancy of opinion among the best histologists of the present day in regard to the minute anatomy of this organ…” [Schmidt 1859, 13] His investigations followed the period between 1830 and 1850 when “the foundations of modern cell biology, of cellular pathology and of normal histology were being laid.” [Bradbury 1967, 204] Schmidt’s full investigation was not published until 1870 due to the Civil War during which his papers were lost in a Washington fire.

Like other investigators whose work he cited, Schmidt created elaborate histological tissue preparations. His paper explains his process for injecting, sectioning and mounting liver tissue from a variety of animals as well as humans. It also describes a microtome that he developed for this process. [Schmidt 1859, 35-40] He also invented tools for studying fresh tissue. Schmidt’s Microscopic Dissector was a refinement of an earlier and simpler mechanism that he had made. This “microscopic needle holder” was essentially a hinged and spring-dampened guide for the sorts of handheld tools that had previously been used in this kind of dissection work.

Schmidt Microscopic Manipulator  3

Schmidt’s Microscopic Needle Holder was a precursor to his micromanipulator [Schmidt 1859, 29-30]

Schmidt’s Microscopic Dissector was a far more elaborate instrument incorporating of several screw-operated mechanisms (“A”) each capable of positioning a metal microtool along three axes.

Schmidt Microscopic Manipulator  1

These mechanisms were mounted on a stable base (“F”) that was clamped to the microscope stage. The sample was placed in a shallow glass-bottomed well (“D”) that contained a clear liquid (usually water.)

Microscopic Manipulator 2

Dissection was performed using needles honed to a fine point on an Arkansas sharpening stone. The needles could be detached and replaced by other tools such as scissors, forceps, and fine scrapers.

Schmidt Microscopic Manipulator  4

The instrument seems to have been reasonably precise; a recent  authority on microtechnique speculates that “There is no doubt that his apparatus could have been used to pick up a single bacterium, had such an idea been possible at the time.” [Bracegirdle 1978, 86] Schmidt’s instrument also embodied limitations that would be resolved by Marshall A. Barber in the early 20th century. The tools faced downwards towards the sample lying on a glass plate rather than upwards towards a sample hanging from a coverslip as in Barber’s arrangement. This meant that the tool tips operated between the sample and the objective, limiting the power of the objectives that could be used. It also meant that as the view of the sample was distorted as the tool tips disturbed the surface of the liquid medium. [Schmidt 1859, 34]

Schmidt’s instrument was developed from his drawings by J. H. Gemrig, a local Philadelphia maker of surgical and dental instruments, and built by  Mr. Wolff, a worker in Gemrig’s shop. Wolff was, in Schmidt’s estimation, “the most accurate workman in his line I have yet met with in this country” . It is not yet clear to me whether Schmidt intended the Microscopic Manipulator for commercial manufacture or whether it was used by others. Schmidt does mention his “old friend Mr. Lüer of Paris”, an instrument maker, as someone likely to improve the instrument. [Schmidt 1859, 36]

Bibliography

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