[Histonet] Dark ground illumination for silver

Rittman, Barry R Barry.R.Rittman <@t> uth.tmc.edu
Thu Mar 24 11:29:47 CST 2005

There are  a lot of material that will show up under darkfield
microscopy, either due to their normal refractile nature or to the
staining process. Silver granules will show beautifully but darkfield is
not specific for silver or for spirochaetes which also show up well.
The only requirement is that materials are able to refract the light
sufficiently so that it will enter the most peripheral portions of the
darkfield condenser, preferably a cardioid condenser.
I often use darkfield for looking at H and E slides.

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Marshall
Terry Dr,Consultant Histopathologist
Sent: Thursday, March 24, 2005 10:28 AM
To: Histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] Dark ground illumination for silver

I don't know why, but all my best stories are against myself. This is
the latest.

I recently had a skin in which there was finely particulate pigment,
rather deep, and slightly but definitely favouring sweat gland basement
membranes. "Ah" thought I - "got it - silver".
The next port of call was microbiology for a darkground microscope.
Delighted I was when the material shone through like the stars in the
desert. As readers may anticipate, that is exactly what silver was
supposed to do.

I sent it to the local centre of excellence for EDAX, having already
spoken to the recipient and telling him that he would be receiving it,
but I was going to do an iron and melanin stain first.
It got neglected, and I suddenly refound it and in a hurry sent it off
without doing these stain.
Yes readers, the report came back that they had stained it for iron and
it was positive.
I have implored the recipient to not tell anyone in exchange for good
money, but I'm sure it will be too late.

So, what is the specificity/range of things that shine through
darkground illumination? I can't find the answer. From the fact that
this test was mentioned for silver, there seemed to me to be an
implication that other common things like iron would not so behave.

Can anyone put me right?

Dr Terry L Marshall, B.A.(Law), M.B.,Ch.B.,F.R.C.Path
 Consultant Pathologist
 Rotherham General Hospital
 South Yorkshire
        terry.marshall <@t> rothgen.nhs.uk

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