Dogs were anesthetized with sodium pentobarbitone (30 mg/kg, intravenously). After tracheotomy, the record of the arterial blood pressure was performed, in the femoral artery. The lateral branch of the tracheal cannula was attached to a Marey apparatus. A cannula was planted in the lateral ventricle and other in the cisterna magna. A electrode was also planted in the brain to record the encephalic temperature. Also, the rectal temperature was recorded. The perfusion was performed with Tyrode solution at 0°C or 39°C. The perfusion at 39°C did not change the brain or rectal temperature. The following modifications were verified with perfusion at 0°C: a) The cerebral temperature decreased until 21°C. No changes were observed in the rectal temperature, b) Respiratory arrest, reversible when the brain was warmed with perfusion at 39°C. c) Vagal stimulation, with fall of blood pressure and bradycardia, which was abolished by atropine.