Quantitative experimental data on the rôle of the sympathetic innervation in the tonus of the quadriceps femoris muscles

Abstract

By the use of Spiegel's method of measuring the tonus of the quadriceps femoris in resting animals, 1 tonus curves of this muscle in cats and dogs were obtained before and after elimination of its sympathetic nerve supply, and before and after removal of the cerebellum. In some of the experiments tonus curves of the same muscle were obtained before and after extirpation of the sympathetic trunk in the lumbar region, in others tonus curves of both quadriceps muscles were obtained in animals which had previously been subjected to unilateral extirpation of the lumbar sympathetic trunk. Removal of the cerebellum was commonly carried out after the tonus curves of both quadriceps muscles were obtained in animals which had been previously subjected to unilateral extirpation of the lumbar sympathetic trunk. Then the tonus curves of both muscles were obtained once more.

These tonus curves are essentially the curves of passive extension of the quadriceps muscles. Those obtained for the same muscle before and after elimination of its sympathetic nerve supply are practically identical with the curves obtained for the muscle on the unoperated and operated sides respectively, following unilateral extirpation of the lumbar sympathetic trunk. The time interval between sympathectomy and the measurement of tonus is relatively unimportant.

Curves which may be regarded as typical of a large number obtained in these experiments are illustrated in the accompanying figure (Fig. 1). The curve of extension of the normal quadriceps (R)

rises very slowly at first, and then more rapidly as the angle of flexion of the knee increases. The quadriceps muscle offers greater resistance at the beginning of passive displacement of the leg from a position of rest in which the knee is only slightly flexed than it does from one in which the angle of flexion of the knee is relatively large.