Experiments (of which 5 are cited) on de-cerebrated cats indicate that the respiratory centre is located in the lower part of the medulla. Respiration is affected by the increase in tonus caused by the activity of the medullary tonus centres when the impulses from the red nucleus are cut off but not deleteriously as long as the vagus nerves are functional. Cutting off of the impulses from the red nucleus and from the lungs by cutting the vagi leads to apneustic respiration. The work of the authors shows no evidence for more than 1 respiratory centre.