Abstract

1. We have determined the latent periods of the stimulation of the medullary centers as a result of decreasing their oxidative processes. This was accomplished by the administration of carbon monoxide or sodium cyanide. The latent periods were found to be so short that the stimulation could not be attributed to the accumulation of acid products. We, therefore, are forced to the conclusion that oxygen want is of itself a stimulus to the medullary centers.

2. We have shown by a direct method that carbon monoxide stimulates the vaso-motor center.

3. The early fall of blood pressure so often produced by carbon monoxide is due to its direct action on the heart.

4. The medullary centers respond to the anoxaemia produced by carbon monoxide, first by stimulation and then by depression.

5. The centers are stimulated and then depressed in the following order: respiratory, vaso-motor and cardio-inhibitory.

6. Support is given to the theory that the activity of the medullary centers depends on the condition of their oxidative processes.

7. A theory is tentatively advanced to account for the stimulation of the medullary centers by oxygen want or decreased oxidation according to which the oxidative processes occurring within the cell are of two types: those not requiring free oxygen, and of which functional activity is the external expression; and those requiring free oxygen and which result in the storing of potential energy and the removal of the products of activity. Stimulation of the latter processes automatically depresses the reactions of activity and depression of the processes characteristic of rest and recovery automatically stimulates those processes of which functional activity is the external expression.