3.8—Core Practical 5 - animal cells and scale

For the animal-cell practical, make a thin, well-prepared slide, observe it systematically with a light microscope, and record only structures that are actually visible. Use a calibrated eyepiece graticule when a scale measurement is required.

Start on low power to locate the specimen safely, then increase magnification for cellular detail. Calibrate the graticule against a stage micrometer at the objective being used; the calibration changes when magnification changes. Make a clear, proportional labelled drawing without shading or invented structures.

If 40 graticule divisions equal 10 μm, one division is 0.25 μm. An object spanning five divisions is therefore 1.25 μm, provided the same objective calibration is still in use.

Image size, actual size and magnification must use compatible units. A plan drawing shows tissue arrangement at low power; a cell drawing shows detail at higher power. Neither replaces the observation itself.