{ diff(x1, t) = (1*k31*(k3*x4*x14 - x1*k4) + 1*k31*((k6 + x8)*x2 - (k5 + x7)*x1))/k31,
  diff(x2, t) = ((-1)*k31*((k6 + x8)*x2 - (k5 + x7)*x1) + (-1)*(k14*x2*x11 - k15*x12)*k31 + 1*k31*k16*k19*x13 + (-1)*k31*(k7 + k18*x10)*x2)/k31,
  diff(x3, t) = 0/k31,
  diff(x5, t) = ((-1)*k31*((k24 + k27*x2)*x5 - x6*k21) + (-1)*k31*k9*x5 + 1*k31*k8)/k31,
  diff(x6, t) = (1*k31*((k24 + k27*x2)*x5 - x6*k21) + (-1)*k31*((k24 + k27*x2)*x6 - k21*x7) + (-1)*k31*k9*x6)/k31,
  diff(x7, t) = (1*k31*((k24 + k27*x2)*x6 - k21*x7) + (-1)*k31*k9*x7)/k31,
  diff(x8, t) = (1*k10*k31 + (-1)*k31*((k25 + k28*x2)*x8 - k22*x9) + (-1)*k31*x8*k11)/k31,
  diff(x9, t) = (1*k31*((k25 + k28*x2)*x8 - k22*x9) + (-1)*k31*k11*x9)/k31,
  diff(x10, t) = (1*k31*x2^2/(k20^2 + x2^2)/k30 + (-1)*k31*x10/k30)/k31,
  diff(x11, t) = (1*k12*k31 + (-1)*(k14*x2*x11 - k15*x12)*k31 + (-1)*k31*k13*x11)/k31,
  diff(x12, t) = (1*(k14*x2*x11 - k15*x12)*k31 + (-1)*k31*((k26 + k29*x2)*x12 - k23*x13))/k31,
  diff(x13, t) = (1*k31*((k26 + k29*x2)*x12 - k23*x13) + (-1)*k31*k16*k19*x13)/k31,
  diff(x14, t) = (1*k1*k31 + (-1)*k31*(k3*x4*x14 - x1*k4) + (-1)*k31*(k2 + k17*x10)*x14)/k31 }