On the -1.9 volt (alternating current) polarographic signal of tissues." A polarographic signal at - 1.9 V (against a saturated-calomel electrode as a reference) is present in extracts of rapidly proliferating animal and plant tissues of normal and cancerous origin. A similar signal was also found in ""germ cells"". The possible lack of this signal in human urine may be helpful for the early detection of neoplasias."