{ diff(x1, t) = (1*k19*k1 + (-1)*k19*k2*x1*x2 + (-1)*k19*k3*x1*(x8 - x2) + (-1)*k19*k4*x1*x4 + (-1)*k19*k5*x1*x3 + (-1)*k9*x1/100*k19)/k19,
  diff(x2, t) = ((-1)*k19*k2*x1*x2 + 1*k19*k3*x1*(x8 - x2) + 1*k19*k12*(x8 - x2) + (-1)*k19*k13*x2)/k19,
  diff(x3, t) = (1*k19*k3*x1*(x8 - x2) + (-1)*k19*k5*x1*x3 + (-1)*k19*k6*x3*x2 + (-1)*k19*k7*x3*x9 + 1*k19*k9*x1/100)/k19,
  diff(x4, t) = ((-1)*k19*k4*x1*x4 + 1*k19*k14*x7 + (-1)*k19*k15*x4 + (-2)*k19*k16*x4^2)/k19,
  diff(x5, t) = (2*k19*k5*x1*x3 + 2*k19*k6*x3*x2 + (-1)*k19*k8*x5 + (-1)*k19*k10*x5)/k19,
  diff(x6, t) = (1*k19*k4*x1*x4 + (-1)*k19*k11*x6 + 1*k19*k15*x4)/k19,
  diff(x7, t) = (1*k19*k9*x1/100 + 1*k19*k10*x5 + (-1)*k19*k14*x7 + 1*k19*k15*x4)/k19,
  diff(x8, t) = 0/k19,
  diff(x9, t) = 0/k19 }