ISCHEMIA plays an important role in the pathophysiology of the nervous system. This paper is an experimental study of the activity induced by ischemia in a definite system, the human A fibers, previously investigated from other points of view1 with the aid of compression by a pneumatic cuff.
If a pneumatic cuff is distended over the site of determination of the systolic pressure on the upper arm, paresthesia in the hand, spreading up toward the wrist, will develop within about a minute. This sensory disturbance is due to the fact that the fibers transmitting light touch are beginning to discharge in the proximal part of the longest ischemic nerve fibers. The ischemia increases the excitability of the nerve, thus precipitating the discharge. When the excitability subsides, owing to the continuation of the ischemia, the paresthesia ceases.
If the calcium content of the blood is reduced, or if its alkalinity