  The NA44 experiment has measured single particle inclusive spectra for
charged pions, kaons, and protons as a function of transverse mass near
mid-rapidity in 158 A GeV/$c$ Pb+Pb collisions.
  From the particle mass dependence of the observed $m_T$ distributions, we are
able to deduce a value of about 120 MeV for the temperature at thermal
freeze-out.
  From the observed ratios of the rapidity densities, we find values of the
chemical potentials for light and strange quarks and a chemical freeze-out
temperature of approximately 140 MeV.
