It has been possible to preserve for more or less time many organs in a living condition when detached from the organism. The organ first tried and which has been most frequently and completely investigated is the heart. This is because of its resistance to any arrest of the circulation and also because its survival is easily shown by its contractility. In man the heart has been seen to beat spontaneously and completely 25 minutes after a legal decapitation (Renard and Loye, 1887), and by massage of the organ its beating may be restored after it has been arrested for 40 minutes (Rehn, 1909). By irrigation of the heart and especially of its coronary vessels the period of revival may be much prolonged. The first experiments with artificial circulation in the isolated heart were made in Ludwig's laboratory, but they were limited to the frog and the inferior vertebrates. Since then experiments on the survival of the heart have multiplied and become classic. Artificial circulation has kept the heart of man contracting normally for 20 hours (Kuliabko, 1902), that of the monkey for 54 hours (Hering, 1903), that of the rabbit for 5 days (Kuliabko, 1902), etc. It has also enabled us to study the influence upon the heart of physical factors, such as temperature, isotonia; chemical factors, such as various salts and the different ions; and even complex pharmaceutical products. Kuliabko (1902) was even able to note contractions in the heart of a rabbit that had been kept in cold storage for 18 hours, and in the heart of a cat similarly kept after 24 hours. The other muscular organs have naturally been investigated in a manner analogous to that which has been used for the heart; and for the same reason, because it can be readily seen whether or not they are alive. The striated muscles survive for quite a long time after removal, especially if they are preserved at the temperature of the body and care is taken to prevent their drying. By this method many investigations have been made of muscular contractions in isolated muscles. Landois has noted that the muscles of a man may be made to contract two hours and a half after removal, those of the frog and the tortoise 10 days after. Recently Burrows (1911) has noted a slight increase in the myotomes of the embryo chick after they have been kept for 2 to 6 days in coagulated plasma.