SUMMARY AND CONCLUSIONS Two groups of 15 dogs each were subjected to five minutes of ventricular fibrillation. Ventricular fibrillation stops all circulation. The brain was, therefore, subjected to a measured period of complete anoxia. The circulation was restored on the second after five minutes. This was done by hand pumping of the heart and by mechanical insufflation of the lungs with oxygen. The coordinated heart beat was restored. One test-group of dogs was given a solution of urea and invert sugar in water intravenously as soon as the period of anoxia was terminated. Otherwise the management of each group of dogs was the same. The conclusion is that intravenous administration of urea, invert sugar and water did not protect the dog after measured periods of cerebral anoxia. The mortality in the treated group was higher than in the untreated group. According to these experiments urea does not have the same beneficial effect as does hypothermia and it is not a replacement for hypothermia after resuscitation of the heart. The effect of hypothermia was published. It was determined in two groups of ten dogs each. The dogs in each series were given either promethazine or chlorpromazine in addition to morphine or meperidine to prevent shivering. There were no recovery dogs in the control group. There were three recoveries in the group under hypothermia and the survival period before death was longer in this group. The results in these two series of dogs, cooled and not cooled, are not the same as in the control series reported in this paper. The conclusion is that promethazine and chlorpromazine contributed to death in each series of dogs. The increased death rate seems to be significantly greater when these drugs were used.