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Techniques & Technologies

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A human embryo, about five days after fertilisation, stained to show details.

A human embryo, about five days after fertilisation, stained to show details.

Credits:Wellcome Library, London.

Scientists had to develop a number of tools and techniques to be able to observe body tissue. First, they needed powerful, reliable microscopes. But it is not enough just to put a small piece of tissue under the microscope. The tissue sample has to be mounted on a translucent slide and be well lit. To make this possible, the tissue has to be cut into very thin slices. In the 1800s scientists developed the microtome, a new instrument that could shave off extremely thin slices from a tissue sample - much thinner even than a slice of Parma ham. Still, a remaining problem might be that all the structures under the microscope are of the same colour, or translucent, so an observer might not be able to distinguish them clearly.

Researchers developed staining techniques to produce a contrast between different objects. In the 1800s chemists had made great advances in developing new synthetic dyes, especially for textiles. Medical scientists tried various substances on tissue samples and found that some chemicals would only stain those components of the tissue which they wanted to observe. At the end of the 1800s the bacteriologist Paul Ehrlich harnessed this discovery and used toxic dyes to combat specific diseases. The first ‘magic bullets’ of modern medicine had been found.