“…I n the animals in which tumour cells were injected intravenously I day after nitrogen-mustard treatment of the limb tumour, it cannot be held that residual circulating nitrogen mustard was responsible for the failure of these cells to form metastases. Nitrogen mustard has a short biological half-life and will not be present in the circulation 24 hours after injection (Ausman and Aust, 1961).…”