Non-muscular organs may also survive a removal from the parent organism, but the proofs of their survival are more difficult to establish because of the absence of movements. Carrel (1906) grafted fragments of vessels that had been in cold storage for several days upon the course of a vessel of a living animal of the same species; in 1907 he grafted upon the abdominal aorta of a cat a segment of the jugular vein of a dog removed 7 days previously, also a segment of the carotid of a dog removed 20 days before; the circulation was reestablished normally; these experiments have, however, been criticized by Fleig, who thinks that the grafted fragments were dead and served merely as supports and directors for the regeneration of the vessels upon which they were set. In 1909 Carrel removed the left kidney from a bitch, kept it out of the body for 50 minutes, and then replaced it; the extirpation of the other kidney did not cause the death of the animal, which remained for more than a year normal and in good health, thus proving the success of the graft. In 1910 Carrel succeeded with similar experiments on the spleen. Taken altogether, these experiments show that the greater part, if not all, of the bodily organs are able to survive for more or less time after removal from the organism when favorable conditions are furnished. There is no doubt but what the observed times of survival may be considerably prolonged when we have a better knowledge of the serums that are most favorable and the physical and chemical conditions that are most advantageous. If we can preserve the organs, we may expect to also keep alive the tissues and cells of which they are composed. Biologists have studied these problems, too, and have also obtained in this department some very interesting results.