QN CE upon a time a person, evidently not a biologist, wrote a jingle to the effect that when his dog Rover died, "he died all over." The rhyme m ay have been correct but the facts were wrong, because certain it is that when Rover's heart stopped beating he didn't die all over; some of his tissues promptly ceased functioning but others did not. This point is of interest to the human race for a number of reasons. Thus, when a man has hanged himself, or has been submerged in water, or exposed to carbon monoxide gas, or has apparently been killed by an electric shock or an overdose of chloroform, the question arises: How soon must the heart be put in motion again if resuscitation is to be effected and ultimate recovery is to be complete? Unfortunately, there have been many cases in which, after artificial respiration had been carried on for a time, the heart and lungs resumed their work but the blood returned too late to the brain, and the patient either remained comatose for several hours and then died or else woke to find later that his brain was badly injured. Much information on this point is to be found in articles by Shillito, Drinker and Shaughnessy, Salinger and Jacobsohn, Bruns, Pike, Guthrie and Stewart, Scheven and Boehm. Some day, when we learn how to prevent the autolysis of transplanted organs, surgeons will be seeking for the best methods of preserving tissues removed from healthy persons who have met sudden death. Already the Russians are experimenting withred blood cells removed from the dead, such cells being kept on ice until needed for transfusion. The subject of survival is of interest also to the histologist when he is securing bits of tissue for study; how long can he wait after the death of the organism before the cells will have changed in their appearance. Or the physiologist who is interested in keeping tissues alive and functioning normally outside the body may want to know how long he can wait before starting a tissue culture. I became interested in survival times because I thought I could probably use differences in death rates of the different tissues of the bowel and perhaps parts of the neurones to analyze the structure and functions of the myenteric plexus. For instance, if it could be shown that synapses are unable to transmit impulses after a certain time, then any function that fails at that time might well be ascribed to conduction through synapses. It was with this idea in mind that the writer searched through much literature for information as to the ways in which different parts of the nervous system die. As everyone knows, the first organ to suffer when the heart stops is the brain; and some parts of it are more sensitive and vulnerable than others. This difference in vulnerability may perhaps be