No subject

As I remember it, the studies showing the marked reduction 
in nerve cell count with age were done around the turn of the
century. Themethod, then as now, is to obtain brains of deceased
persons, fix tehm, prepare cuts, count cells microscopically
in those cuts, and then estimate the total number by multiplying
the sampled cells/(volume of cut) with the total volume.

This method has some obvious systematic pitfalls, however.
The study was done again some (5-10?) years ago by a German
anatomist (from Kiel I think), who tried to get these things
under better control. It is well known, for instance, that
tissue shrinks when it is fixed; the cortex's pyramidal cells 
are turned into that form by fixation. The new study showed
that the total water content of the brain does vary dramatically 
with age; when this is taken into account, it turns out that 
the number of cells is identical within error bounds (a few 
percents?) between quite young children and persons up to 
60-70 years of age.

All this is from memory, and I don't have access to the 
original source, unfortunately; but I'm pretty ceratin that
the gist is correct. So the conclusion seems to be that the
cell loss with age in the CNS is much lower than generally
thought. 


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