Thanks for all the responses.
I now have corroborating testimony from the Mathematica list that:
"There is not a general analytical solution for a system of ODEs with 3
or more variables where all coefficients are parameters"
Other suggestions were: fixing some coefficients, getting the steady
state solution, or getting a truncated Taylor series solution.
The first two may work for certain special cases, but I would like to
use the solution to simulate behavior over a wide range of conditions
(parameter values) and times, so it would be tedious to get a new
solution for every case. I'm not sure how to approach the last
suggestion, but I'm looking into it.
I've also found that others tend to solve these "compartmental" systems
with the numerical Runge-Kutta algorithm or similar.
Regards,
Neil
--
______________________________________________________
Neil E. Klepeis, UC Berkeley, School of Public Health,
and Lawrence Berkeley National Laboratory,
Berkeley, CA USA. Voice: 831-768-9510