Fish-plates and Frog-plates: Live Examination Under the Microscope

During the last years of the 17th century many people speculated about the future and importance of the microscope. Some thought that it had shown all it could, and some recent historians have accepted this view. In spite of this, some important discoveries were still being made, such as the existence of capillaries. Microscopes sold in the early 18th century often included a 'frog-plate' or 'fish-plate', so that anyone could view these tiny blood vessels.

The years immediately following the Second World War saw the development of the first 'computers' as we know them today: digital, electronic, programmable calculating machines. Some of the most important early work in digital electronic computing was carried out in Cambridge during the post-war years. One of the first stored-program computers, the EDSAC, was developed by the University Mathematical Laboratory.

Computing coming of age

In the years between the two world wars, an explosion of research into electromechanical automation, along with a healthy dose of ingenuity, led to the development of electronic digital computers. In the early days, 'automatic' computers, such as Konrad Zuse's Z3 and Howard Aiken's Harvard Mark I, used electric relays and rotating wheels similar to the ones in adding machines.

Electronic computers made with vacuum tubes - which made them much faster - were the next development, and were a major strategic component of World War II. While the U.S.-made Electronic Numerical Integrator and Computer (ENIAC) was announced to much fanfare, the British government had actually built an earlier computer called Colossus. This had been kept hidden for decades, due to its origins in the wartime code-breaking work undertaken at Bletchley Park.

Early computers hardly resemble the machines we use today. They were mainly designed, like Babbage's Analytical Engine, to solve complex mathematical problems. Additionally, they had to be physically set up with a hard-wired program - switches and parts moved into place depending upon the calculation - and have instructions fed to them continually.

The major achievement that brought about the modern computer was the invention of the stored program: instructions that are stored in a computer's electronic memory. The first computer to have this feature was the University of Manchester's Small-Scale Experimental Machine, or "Baby." However, the first stored-program computer to go into regular use was Cambridge University's Electronic Delay Storage Automatic Calculator (EDSAC) in 1949.

Until the 1970s, most calculating devices were constrained by either the limited number of tasks that they could perform or by their extravagant size and cost. Advances in integrated circuit research would prove to be the solution to both these problems, enabling the manufacture of miniaturised electronic calculators that were both flexible computing machines and, within a relatively short period of time, affordable to most.

The Whipple Museum is in possession of over 400 pocket electronic calculators, a collection assembled by Cambridge architect, Francis Hookham. You can download a fully illustrated catalogue of the Museum’s ‘Hookham Collection’ using this link:

Download Multiply: The Francis Hookham Collection of Hand Held Electronic Calculators (pdf)

Making microchips

In 1968, Hewlett-Packard (HP) released its HP 9100A, the first fully electronic desktop calculator: a limited yet powerful computer for its time. About the size of a typewriter and costing a whopping $4,900, it found its way into the pages of tech visionary Stewart Brand's Whole Earth Catalog, advertised next to beads and moccasins as the 'machine of the future'. Bill Hewlett congratulated his calculator design team on their achievement, but immediately set them to work on a model that was affordable and could fit in a shirt pocket.

At the same time, Texas Instruments (TI) and Sharp Electronics had also jumped into the race to make a miniaturised calculator using only four or five 'integrated circuits'. These 'microchips' (as they are now known) are small plates of semiconductor material composed of transistors and other tiny components which replaced discrete circuits made of large vacuum tubes and resistors.

A new electrical engineering company, Intel, was commissioned to make a 'microchip' for calculators manufactured by another Japanese company, Busicom. Intel bought back the rights to this chip in 1971 and began selling the Intel 4004, the world's first commercially available microprocessor, which launched a great number of developments in microelectronics that quickly swept through the computing industry.

Blood circulation

The circulation of blood was only fully understood during the 17th century. William Harvey (1578-1657) proposed the circulation of blood, based on his dissection work on the heart. Whilst Harvey's theory became generally accepted, it had one major flaw: he could not account for the movement of blood between arteries and veins, and for his theory of circulation to make sense this movement was necessary. Circulation was only fully understood after Harvey's death, when Marcelo Malpighi and Antoni van Leeuwenhoek observed capillaries, tiny blood vessels that carry the blood between arteries and veins.

A microscope capable of magnifying roughly 100 times is capable of showing capillaries, and at the beginning of the 18th century these microscopes were becoming available for interested and educated members of the public. Microscopes were often sold with a selection of prepared slides, and also with a 'frog-plate' or 'fish-plate'. The Whipple Museum has three such accessories, which allow a fish or a frog to be strapped down for observation. On this page are examples of glass and brass frog-plates.

Once the frog or fish tied down, capillaries can be seen in the leg or fin as long as a sufficiently strong light is shone through the animal.

Microscope demonstrations

It remains unclear how widely these accessories were used. They would have been less convenient to use than the slides that were sold. To use the frog-plate an animal would have to be caught and then tied down live or recently-deceased. Most frog-plates held in museums demonstrate no obvious evidence of use. However, the frog-plate remained a selling point for the microscope. Public demonstrations of microscopes became increasingly popular during the 18th century, and frog-plates may well have been used at these organised events rather than by interested amateurs at home.

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