DII~AC (1) demonstrated long ago that the existence of magnetic monopoles together with the formalism of quantum mechanics necessarily implies that the sources of the electromagnetic field (electric and magnetic charge) are quantized. Several different arguments leading to Dirac's conclusion have been put forth, notably those due to SC~WI~G~n (2) and CABIBBO and I~ERRARI (a). The method of the latter two authors has the distinct advantage of relativistic covariance. Recently MOTZ (4) has adapted Schwinger's line of reasoning to general relat ivi ty in an a t tempt to demonstrate the quantization of the source of the gravitational field; that is the quantization of mass. The val idi ty of his procedure is open to some criticism as he employs only an approximate two-body equation of motion in his derivation; in addition, the covariance of his result is not clear. The method of CAmnBO and FERRARI in the case of electromagnetism is equivalent in its conclusions to that of SCHWINGER and, in addition to possessing covarianee, their method does not require the use of the equations of motion of the field sources. Therefore, it is the purpose of this note to investigate their procedure as applied to the gr~vitationM field. To this end consider the Dirac equation for a spinor field in curved space