{ diff(x1, t) = 0,
  diff(x2, t) = (1*k2 + (-1)*(k3 + k4*x4 + k5*x5)*x2)/k55,
  diff(x3, t) = 0,
  diff(x4, t) = (1*k6 + (-1)*(k7 + k8*x5)*x4)/k55,
  diff(x5, t) = (1*(k9 + k10*x24)*(k13 - x5)/(k12 + k13 - x5) + (-1)*k11*x2/(1 + k54)*x5/(k12 + x5))/k55,
  diff(x7, t) = (1*k14 + (-1)*(k15 + k16*x4)*x7)/k55,
  diff(x9, t) = (1*k17 + (-1)*k18*x9)/k55,
  diff(x11, t) = (1*(k19*x8*x10 - k20*x11) + (-1)*(k15 + k16*x4)*x11 + (-1)*k18*x11)/k55,
  diff(x12, t) = (1*(k21*x24 + k22*x22)*x23/(k25 + x23) + (-1)*(k23*x2/(1 + k54) + k24*x21)*x12/(k25 + x12 + x13) + (-1)*k26*x12*x24 + 1*k27*x13)/k55,
  diff(x13, t) = (1*k26*x12*x24 + (-1)*k27*x13 + (-1)*(k23*x2/(1 + k54) + k24*x21)*x13/(k25 + x12 + x13))/k55,
  diff(x14, t) = (1*k30 + (-1)*(k31 + k32*x5)*x14)/k55,
  diff(x15, t) = (1*(k33 + k34*x2/(1 + k54))*(x14 - x15)/(k36 + x14 - x15) + (-1)*k35*x15/(k36 + x15) + (-1)*(k31 + k32*x5)*x15)/k55,
  diff(x17, t) = (1*(k37 + k38*x15)*(k42 - x17)/(k41 + k42 - x17) + (-1)*(k39 + k40*x22)*x17/(k41 + x17))/k55,
  diff(x19, t) = (1*(k43 + k44*x24)*(k50 - x19)/(k47 + k50 - x19) + (-1)*(k45 + k46*x2/(1 + k54))*x19/(k47 + x19))/k55,
  diff(x21, t) = (1*k48*(x17 - x21)*(x19 - x21) + (-1)*k49*x21 + (-1)*(k39 + k40*x22)*x21/(k41 + x17) + (-1)*(k45 + k46*x2/(1 + k54))*x21/(k47 + x19))/k55 }