{ diff(x1, t) = (1*k14*k1*x1*(1 - x1/k2) + (-1)*k14*k3*x1*x2)/k14,
  diff(x2, t) = (1*k14*k3*x1*x2 + (-1)*k14*k4*x2 + (-1)*k14*k5*x2)/k14,
  diff(x3, t) = (1*k13*k6 + (-1)*k7*x2*x3 + (-1)*k13*k8*x3)/k13,
  diff(x4, t) = (1*k7*x2*x3 + (-1)*k13*k8*x4 + (-1)*k13*k10*x4 + (-1)*k13*k9*x4)/k13,
  diff(x5, t) = (1*k13*k9*x4 + (-1)*k13*k8*x5)/k13 }