In two series of experiments made at the end of 1911 and at the beginning of 1912, new techniques were developed with the view of investigating the problem of prolonging indefinitely the life of tissues isolated from the organism. These techniques are far from perfect and will doubtless be modified in the future. But they have already permitted the establishment of new facts. Fragments of connective tissue have been kept in vitro in a condition of active life for more than two months. As a few cultures are now eighty-five days old and are growing very actively, it is probable that, if no accident occurs, the life of these cultures will continue for a long time. In some cases the rate of growth of the tissues increased in direct ratio to the age of the culture. Fragments of heart pulsated rhythmically at the beginning of the third month of their life in vitro. These facts show that experiments made with these or with more perfect techniques and followed over long periods of time may lead to the solution of the problem of permanent life of tissues in vitro, and give important information on the characters acquired by tissues liberated from the control of the organism from which they were derived.