To give a clear idea of the meaning of latency, we must point to a few biologic facts in relation to the invasive stage of syphilis. After a given infection, when the virus is deposited on an abraded surface, the organisms begin to proliferate and are wafted quickly into the general circulation, as has been actually demonstrated by Brown and Pearce 1 and one of us.2 The organisms continue to increase at the site of the lesion and probably within the body until the period of multiple systemic localization occurs. When the spirochetes are planted in the tissues and organs of the body, colonies are formed and through their growth and life cycle induce certain biochemical changes which may be exhibited in all organs; and, no matter where located, seem to stimulate the same cellular reaction. They arrive by way of the blood stream in these various organs and especially in the skin where they continue proliferation. Their presence induces at these points of colonization the formation of lymphoid cells, plasma cells and new connective-tissue cells and sometimes giant cells (a papule), but the organism exerts little attraction for the polymorphonuclear leukocytes. The new-formed cells have not the power of reorganization and have a tendency toward résorption and disin-Studies, reports and observations from the