Preparing Tiny Samples for Microscopy, & Home-Made Dissecting Needles
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I don’t suggest that this will work for every situation or sample, but one technique I use which works quite well with some tiny fungi is to use a second microscope slide, both to hold the sample, and as a “cutting guide” for the scalpel/razor blade. (It also works quite well for cutting cross sections of leaves to look at paraphyses in rust sori). Under the stereo scope, I will position the sample on a microscope slide using dissecting needles.
I use home made dissecting needles which are much thinner and sharper than ones usually found on sale. These are made up from very fine sewing needles stuck into 100mm lengths of 6mm wooden dowelling – (I simply cut the dowel to length, fine-sand-paper the cut ends, and, whilst firmly holding the needle with pliers, carefully push the “eye end” into the end of the dowel. No need for making any pilot holes, and no need for glue etc. – See photo below
Once the sample is oriented how I want it, I then bring in a second slide, and, whilst still holding the sample in position with a needle, rest the second slide partially on top of the sample, along the line of where I want to cut it.
Then, whilst (gently) holding the sample in place with the second slide, I can take the dissecting needle away, leaving that hand free to use the blade.
I then use the edge of the uppermost microscope slide as a blade “rest” to position the blade against, and guide the cut.
The process can then be repeated, by manipulating the sample into position for a second cut, to (hopefully) finish up with a thin section.
I find that using a microscope slide to hold the sample whilst cutting tends to work better than holding it with a needle, as it helps to stop the sample from rotating when starting the cut, and steadies the blade into the exact cutting position much more easily than using the blade entirely “freehand”.
Worth also mentioning that scalpel/razor blades always seem to cut better if dipped in water immediately before making the cut.
I sometimes also put a drop of water on the sample itself, before cutting, once it is trapped in position by the upper microscope slide.
[attachment=0]Dissecting Needles.jpg[/attachment] Regards,
Mike.
A good tip Mike! I am no woodworker but managed to prepare these fine dissecting needles in no time and they do the job. Two bits of wood cut with a Stanley knife from some spare floorboarding in the cellar – just slice of the edge where it inserts into the adjacent floorboard. Then get a couple of fine dress-making pins from the wife’s pin-cushion. Snip the ends of the pins with the wirecutting part of some pliers (watch your eyes as the heads fly off). Get a biggish needle and use pliers to make a guide hole in the end of the wood pieces (gripped in your WorkMate), about half a cm deep. Push in the pins cut end first, and put a drop of Gorilla Glue around the junction. Keep them in a safe place – I use a lump of Plasticine stuck to the dissecting microsope.
Then you’re ready to tease apart crust and polypore tissue
Steve
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