{ diff(x1, t) = ((-1)*k19*k2*x1*x2/(1 + (x2/k18)^k17) + 1*k19*k1)/k19,
  diff(x2, t) = ((-2)*k19*k2*x1*x2/(1 + (x2/k18)^k17) + 1*k19*(k4*k6*x4*x5*(k15 - x2) - k5*k7*x6*x2*(k16 - x5))/(k5*(k16 - x5) + k6*(k15 - x2)) + 1*k19*k8*x6*(k15 - x2) + (-1)*k19*k11*x2)/k19,
  diff(x3, t) = (1*k19*k2*x1*x2/(1 + (x2/k18)^k17) + (-1)*k19*k3*x3)/k19,
  diff(x4, t) = (2*k19*k3*x3 + (-1)*k19*(k4*k6*x4*x5*(k15 - x2) - k5*k7*x6*x2*(k16 - x5))/(k5*(k16 - x5) + k6*(k15 - x2)) + (-1)*k19*k12*x4*(k16 - x5))/k19,
  diff(x5, t) = ((-1)*k19*(k4*k6*x4*x5*(k15 - x2) - k5*k7*x6*x2*(k16 - x5))/(k5*(k16 - x5) + k6*(k15 - x2)) + 1*k19*k12*x4*(k16 - x5) + 1*k19*k10*x8*(k16 - x5))/k19,
  diff(x6, t) = (1*k19*(k4*k6*x4*x5*(k15 - x2) - k5*k7*x6*x2*(k16 - x5))/(k5*(k16 - x5) + k6*(k15 - x2)) + (-1)*k19*k8*x6*(k15 - x2))/k19,
  diff(x7, t) = (1*k19*k8*x6*(k15 - x2) + (-1)*k19*k9*x7)/k19,
  diff(x8, t) = (1*k19*k9*x7 + (-1)*k19*k14*(x8 - x9) + (-1)*k19*k10*x8*(k16 - x5))/k19,
  diff(x9, t) = ((-1)*k19*k13*x9 + 1/10*k19*k14*(x8 - x9))/k19 }