{ diff(x1, t) = (1*k19*k1/k19 + 1*k19*k2*x2^k3/(k4^k3 + x2^k3)/k19 + (-1)*k19*k5*x1)/k19,
  diff(x2, t) = (1*k19*k13*x5 + (-1)*k19*k15*x4*x2 + 1*k19*k14*x5 + 1*k19*k16*x5 + 1*k19*k17*x5/(k11 + x3 + 2*x4 + 2*x5)/k19)/k19,
  diff(x3, t) = (1*k19*k6*x1 + (-1)*k19*k7*x3 + (-2)*k19*k8*x3^2 + 2*k19*k9*x4 + (-1)*k19*k10*x3/(k11 + x3 + 2*x4 + 2*x5)/k19 + (-1)*k19*k12*x3)/k19,
  diff(x4, t) = (1*k19*k8*x3^2 + (-1)*k19*k9*x4 + 1*k19*k13*x5 + (-1)*k19*k14*x4 + (-1)*k19*k15*x4*x2 + (-1)*k19*k17*x4/(k11 + x3 + 2*x4 + 2*x5)/k19 + (-1)*k19*k12*x4)/k19,
  diff(x5, t) = ((-1)*k19*k13*x5 + 1*k19*k15*x4*x2 + (-1)*k19*k14*x5 + (-1)*k19*k16*x5 + (-1)*k19*k17*x5/(k11 + x3 + 2*x4 + 2*x5)/k19)/k19 }