Posted in February 2019

It’s now over a year since I described how to use the Abbe polarizing attachments with one of our late 19^th century jug-handled microscopes. Since then, I’ve had one disappointment. The attachment does not fit any of our more “modern” (ie 20^th century, with electricity) microscopes and I’ve had to continue using the mirrored model.

My original attempts to use them all employed thin mineral slices because I wanted samples with known, reliable reactions to the polarizing light, but then I started considering what they were actually used for in Microbiology or Botany laboratories.  We have at least 20 of the adaptors, plus a number of partial or damaged kits, so they must have originally been used for teaching before WW1. It seemed a good idea to test their performance with biological samples.

In all of the image pairs presented here, the first image is without polarization, and the second with it.

The first image set (above) shows two of my standard microscope-testing samples (very useful for comparisons). The insect is a lacewing and the sample came from one of its wings. Despite the fact that the lacewing has been dead at least 2 years (it was “rescued” from a spider’s web), the veins gave clear, silvery-white fluorescence with polarising light. The thin section is a commercially bought, stained section of a plant stem. From comparisons with other samples, it is the stains that fluoresce, not the fixed plant tissue.

The remaining images (above) were made with living algae (Closterium sp.) at 2 magnifications (Zeiss lenses C and D, but their magnifications need to be recalibrated because of the distance of the camera’s sensor from the lens). It appears that only sections of their chloroplasts were fluorescing. The sample had been taken a week previously from a pond in the area where the Berkelsemeer (Van Leeuwenhoek’s first microbial hunting ground) used to be.

Guessing from the location of the cupboards where we found the attachments, it seems likely that they belonged to the Botany department. We’ve recently found a few of their practical handbooks in the archive – maybe one day I’ll be able to try the attachments with the original experiments! First, I want to try the other microscopes in our collection.