{ diff(x1, t) = (1*k28*k1*x1*(1 - x1/k2) + (-1)*k28*x1*(k16*0 + 1/5*k16/(k18*k17^2)*x2^2) + (-1)*k28*(k11*x4 + k3)*x1)/k28,
  diff(x2, t) = (1*k28*0*k17 + (-1)*k28*k18*x2)/k28,
  diff(x3, t) = (1*k28*k4*(k26*x6/(x1 + x6) + k11*x4 + k3)^2/((k26*x6/(x1 + x6) + k11*x4 + k3)^2 + k14^2)*(x1 + x6)/((k26*x6/(x1 + x6) + k11*x4 + k3)^2/((k26*x6/(x1 + x6) + k11*x4 + k3)^2 + k14^2)*(x1 + x6) + k5) + 1*k28*(1 - x5/(1 + k27/k22))*(1 - (k26*x6/(x1 + x6) + k11*x4 + k3)^2/((k26*x6/(x1 + x6) + k11*x4 + k3)^2 + k14^2)*(x1 + x6)/((k26*x6/(x1 + x6) + k11*x4 + k3)^2/((k26*x6/(x1 + x6) + k11*x4 + k3)^2 + k14^2)*(x1 + x6) + k15))*x3*(k7 - k8) + (-1)*k28*k9*x3)/k28,
  diff(x4, t) = (1*k28*(1 - x5/(1 + k27/k22))*(1 - (k26*x6/(x1 + x6) + k11*x4 + k3)^2/((k26*x6/(x1 + x6) + k11*x4 + k3)^2 + k14^2)*(x1 + x6)/((k26*x6/(x1 + x6) + k11*x4 + k3)^2/((k26*x6/(x1 + x6) + k11*x4 + k3)^2 + k14^2)*(x1 + x6) + k15))*x3*k8 + (-1)*k28*k10*x4)/k28,
  diff(x5, t) = (1*k28*k13*x4/(k12 + x4) + (-1)*k28*k13*x5)/k28,
  diff(x6, t) = (1*k28*x1*(k16*0 + 1/5*k16/(k18*k17^2)*x2^2) + (-1)*k28*k26*x6)/k28 }