Slide Preparation

How were the microscope slides prepared? This is a significant question because slide preparation would be different depending on what the researcher was expecting to see. Unfortunately I have been unable to find any information on how these slides were created. Unseen says only that the slides were prepared by Dr Robert Lawrence. However, it is unlikely that he personally prepared the slides, more likely they were prepared by a technician in his lab.

If they were just asked to take a quick look at an unknown specimen, and the specimen was not particularly solid, so it could be smushed on the slide, it’s possible they just did a quick wet mount, placing a small amount of the tissue in a drop of water or mounting media on the slide, and placing a cover plate over it, and then stained it.

If they treated it like a histology sample, it would be first fixed by treating it with a chemical like formalin to prevent it from decaying. Then they would dehydrate it with alcohol, treat it with xylene, and embed it in paraffin wax. Then they would take thin slices of the paraffin wax to mount on the slides, and stain them.

If they suspected it was fungus, they would first try to culture it – grow a sample of the spores in a petri dish full of nutrients. This would allow them to examine young, actively growing material, because older colonies are often unrecognizable. A sample would be taken with a needle and teased apart in a droplet of water or mounting media.

What stains were used?

Then they applied stains to highlight the structures of the cell. Based on the images, stains were used which stain the nuclei a dark colour, and the extracellular matrix and cytoplasm red. This was likely hematoxylin and eosin, or an H&E stain, because that’s ubiquitous in pathology labs, although some people I asked to examine the images noted that the colour of the stains seemed off, and there are other stains that do the same thing. The consistent message I got from people I asked to examine the slides was that the staining job was poorly done[1], making it difficult to get a good look at the intracellular structures. This makes me think that the slide preparation was probably done quickly, and may have been a simple wet mount.

[1] Note that this was before anyone had seen my at-home staining job, which set a new low bar