BEGINNING in 1944 and in the ensuing years we have been active in the investigation of the problems of arterial homografts. Early in this work we felt the need for some method for preserving such grafts for use at a time considerably after their removal. Initially, we advocated the use of rapidly frozen grafts and showed that such grafts could be kept for prolonged periods of time at temperatures of -70 C.* Later the rapid freezing process was supplemented by drying in the frozen state,3 and after this we devised the method for the sterilization of such grafts with the use of ethylene oxide, both as a liquid and as a gas.4 The culmination of this process has therefore been the use of freeze-dried grafts which can be kept indefinitely in sealed vacuum tubes after being taken without aseptic precautions.
For the past two years all the homografts