The word anesthesia-means WITHOUT FEELING. This describes accurately the effect of ether in the anesthetic dosage. Although there is no pain felt during operations when anesthesia is inhaled, the *nerve impulses excited by a surgical operation still reaches the brain. Not every portion of the brain is fully anesthetized, since surgical anesthesia does not kill and this allows the nerve impulses to reach the brain. This gives rise to the question : What will be the effect of trauma upon the part of the that remains awake? If in surgical anesthesia, the traumatic impulses cause an excitation of the wide-awake cells, how are the remainder of the cells of the brain, despite anesthesia, affected? Also, are they prevented by the anesthesia from expressing that influence of nerve stimulus in conscious perception or in muscular action.
Whether the ANESTHETIZED cells are influenced or not must be determined by noting the physiologic functions of the body after anesthesia has worn off. This can be done in animals by an examination of the brain-cells. The effect of Anesthesia on the vasomotor, the cardiac, and the respiratory centers discharging energy in response to traumatic stimuli applied to various sensitive regions of the body during surgical anesthesia have long been known. If the trauma is more, exhaustion of the entire brain will be observed after the effect of the anesthesia has worn off. In spite of the complete paralysis of voluntary motion and the loss of consciousness due to ether, the traumatic impulses that are known to reach the AWAKE centers in the medulla also reach and influence every other part of the brain.
The functional depression which is a consequence of the morphologic alterations seen in the brain-cells may be due to the low blood-pressure which follows excessive trauma is shown by the experiments. The circulation of animals was first rendered STATIC by over-transfusion, and was controlled by a continuous blood-pressure record on a drum. In each of the instances, morphologic changes in the cells of all parts of the brain were found, but it required much more trauma to produce brain-cell changes in animals whose blood-pressure was kept at the normal level than in the animals whose blood-pressure was allowed to take a downward course. In the cortex and in the cerebellum, the changes in the brain-cells were in every instance more marked than in the medulla.