{ diff(x1, t) = 1*k26*k1*x3^k11*(1 - x1/k8)/k26,
  diff(x2, t) = (1*k26*k2*x1^k12*(1 - x1/k8)*k13 + 1*k26*k3*x2^k14*(1 - x1/k8) + (-1)*k26*k4*x2^k19*x4^k20 + (-1)*k26*k5*x2)/k26,
  diff(x3, t) = ((-1)*k26*k1*x3^k11*(1 - x1/k8) + 1*k26*k4*x2^k19*x4^k20 + (-1)*k26*k6*x3^k21)/k26,
  diff(x4, t) = (1*k26*k7*x1^k15*x2^k16*(k23 + x3)^k17*(1 - x1/k8)^k18 + (-1)*k26*k24*x4^k22)/k26,
  diff(x5, t) = ((-1)*k26*k9*x4 + 1*k26*k10*x3)/k26 }