  We consider a spin coherent states description of a general quantum spin
system. It is shown that it is possible to use the spin-1/2 representation to
study the general spin-J case. We identify the 1/2 spinor components as the
homogeneous coordinates of the projective space associated to the complex
variable that labels the coherent states and establish a relation between the
two-component spinor and the bosonic Schwinger representation of a spin
operator. We rewrite the equations of motion, obtained from the path integral
for the evolution operator or partition function, in terms of the 1/2 spinor
and define the effective Hamiltonian of its evolution.
