THE RELATION OF THE SYMPATHETIC NERVOUS SYSTEM TO THE CONTRACTIONS AND FATIGUE OF SKELETAL MUSCLE IN MAMMALS

Abstract

When the M. tibialis anticus, in cats with a normal circulation, is contracting as a result of a series of single induction shocks applied to the anterior spinal roots, superadded stimulation of the abdominal sympathetic chain may cause either an increase or decrease in the height of the contractions. The decrease is due to vasoconstriction. The increase is not due to an increase in blood supply nor to any substance which may be carried by the blood, such as adrenalin, but must be due to stimulation of nerve fibers in the sympathetic chain other than the vaso-motors, the impulses from which affect the muscle in some unknown manner, producing an increase in contraction height. When the vasoconstrictor fibers are paralyzed by the use of ergotoxin, stimulation of the sympathetic chain causes only an increase in the series of contractions. The experiments, therefore, confirm, in mammals with normal circulation, the results of Orbeli''s experiments on the bloodless muscles of frogs.