[OS X TeX] Why is cmr10.tfm not being used?

[Doug McKenna]

All -

I'm running:
  TeXLive 2010
  TeXShop 2.36
  MacOS 10.6.8

My entire MWE source file (FontTest.tex) is:

\tracingassigns=1
\tracingonline=1
\font\fontname=cmr10.tfm
\fontname
\bye

Runnnig TeX under either plain or LaTeX format, or with DVI output or 
not, the log file is

This is pdfTeX, Version 3.1415926-1.40.11 (TeX Live 2010) (format=pdftex 
2011.2.17)  4 SEP 2012 21:27
entering extended mode
 \write18 enabled.
 file:line:error style messages enabled.
 %&-line parsing enabled.
**FontTest.tex
(./FontTest.tex{into \tracingassigns=1}
{changing \tracingonline=0}
{into \tracingonline=1}
{changing \fontname=\fontname}
{into \fontname=select font nullfont}
{reassigning current font=\fontname}
 )
No pages of output.
PDF statistics:
 0 PDF objects out of 1000 (max. 8388607)
 0 named destinations out of 1000 (max. 500000)
 1 words of extra memory for PDF output out of 10000 (max. 10000000)

My question is: Why is it defining \fontname to be "select nullfont"?  I 
thought "cmr10.tfm" was pretty basic and always available.  And if not, 
why isn't it telling me it's not finding what I thought I wanted it to 
use?

Here's the search for the TFM file, which finds it here:

find /usr/local/texlive -name cmr10.tfm -print
/usr/local/texlive/2010/texmf-dist/fonts/tfm/public/cm/cmr10.tfm

Thanks in advance for any info or explanation of a misunderstanding on my 
part. 



Doug McKenna