One of the chief obstacles preventing definite location of the source of the testicular hormone has been the fact that the several types of tissue in the testis have been inseparable. Only a few authors have been bold enough to state that in their experiments only one type of tissue remained, the other tissues having degenerated. Always in addition to interstitial cells there have been present Sertoli cells and in most cases also spermatogonia. A few workers have claimed partial degeneration of Sertoli cells, but their evidence lacks conviction. As Whitehead1stated, only when we can definitely eliminate each type of tissue will the problem be solved. In seeking a method of eliminating each type of tissue in the testis, it occurred to me to use the cytolysin or antibody production method. In this way, it was hoped that a specific antibody for the germ cells might be produced