RSRICHMOND@aol.com wrote:
> 
> ups and downs, in general the slides are a great deal better than they were
> when I was a resident. I have the abiding suspicion that improved embedding
> media are the biggest single reason for this improvement.

I wonder if this is really so. In the late 1970s Russ 
Allison did a comparative study of over 100 different waxes, 
additives etc:

  Allison, RT. The crystalline nature of histology waxes: a
preliminary communication. Med Lab Sci 35: 355-363.
  Allison RT. The crystalline nature of histology waxes: the 
effects of microtomy on the micro-structure of paraffin 
wax sections. Med Lab Sci 1979; 36: 359-372.

He found that they were all pretty much the same. I don't
think the proprietary waxes like Tissuemat and Paraplast
have changed since before the 1970s. Here we used to mix
one of these with 2 volumes of Parowax, a cheap domestic
paraffin sold in stores for making candles, putting on
top of home-made jam etc. (Parowax alone was just a little
too hard for easy sectioning, or so the experienced chief
technician told me; I never tried it myself, but used the
mixture a lot in those days.)

-------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan/