For a single-component perfect Fermi gas we used the numerical programs for the equation of state given by Bauer. For a star of hot non-degenerate neutron gas we calculated the deviations of the internal structure with regard to a totally degenerate neutron star. For a multi-component perfect gas with an exponential-type elementary particle spectrum we present the equation of state. The highest possible temperature is T_0=2*10^12°K, where the total mass density diverges. For the central region of hyperon stars, in contrast to other authors, we can prove that the time component of the metric tensor has no singularity, and that the velocity of sound tends to zero ( instead of rising above the velocity of light ).