Studies of Accommodation of Nerve in Parathyroid Deficiency.

The properties of human nerve change with variations in the chemical content of the body fluids. When this change is pronounced, the altered condition of the nervous tissue is readily observed, as in tetany due to hypocalcemia or marked alkalosis. A quantitative measure of the condition of the nerves could be used to determine less obvious but perhaps significant variations in the functional characteristics of nerve. Such measurements would reveal the graded changes in nerve tissue associated with the gradual changes in the blood chemistry. The purpose of the present studies is to test the usefulness of a quantitative index of the changes in human nerve that accompany variations in the calcium ion concentration in the body fluids. The property of nerve employed is the rate of accomodation to an electrical current. The process of accomodation can be described briefly as follows. The minimum constant current which just stimulates a nerve is called the rheobase. When the stimulating current rises slowly to its final value, the threshold strength of the current is greater than the rheobase. The slower the rate of rise of the current the higher is the threshold value. The property of a nerve by which it thus adjusts to the gradual development of the stimulating action of an electric current is called accomodation. This property is markedly altered in excised nerves by variations in the concentration of ionized calcium in the fluids bathing the tissue (1). Furthermore, it can be readily measured in man as has been shown (1). An opportunity to study the variations in this property of human nerve in 5 cases of hypoparathyroidism was provided through the cooperation of the Medical Service of the Hospital of the University of Pennsylvania.2