[texhax] A macro needed for small italics shape relative to the main bodu text size

[swami at mun.ca]

I need to write a macro, say \sit (for small italic size)
so that \sit{xxxx} should put the "xxxx" in a smaller italic
shape "relative to" the body text font size (and not an absolute small italics
size). If I write the macro as follows

\newcommand{\sit}[1]{{\footnotesize\itshape #1}}

it works fine if the body font is \normalsize, but if the body 
text size is reduced to \small, \tiny, or \footnotesize, 
the \sit{xxxx} command does not produce a proportionately smaller 
italic font, but keeps its original size as it was using before, 
when working with normalsize body text.

How can I change the above macro so that \sin{xxxx}  puts 
a "smaller italic" shape "relative to the body font used, and not an
"absolute small italics"?