Quantitative experimental data on the sympathetic innervation and tonus of triceps brachii muscles.

Abstract

In a recent paper 1 the writers reported briefly the results of tonus measurements on the quadriceps femoris muscles in cats and dogs, obtained by the use of Spiegel's method, 2 before and after elimination of the sympathetic nerve supply to these muscles, and before and after removal of the cerebellum. By the use of the same method, tonus measurements of the triceps brachii muscles in cats and dogs were obtained before and after elimination of their sympathetic, and before and after elimination of their somatic nerve supply.

The tonus curves, i. e., the curves of passive extension, of the triceps brachii, obtained under comparable conditions, are similar to those of the quadriceps femoris. However, the components of tonus mediated through the sympathetic and the somatic innervation, respectively, can be studied more advantageously in the triceps than in the quadriceps, by reason of the fact that either the sympathetic or the somatic nerve supply to the former may be cut off, leaving the other intact. In the case of the quadriceps the sympathetic supply may be cut off without impairing the somatic, but the somatic supply may not be cut off without impairing the sympathetic. In our experiments the sympathetic nerve supply to the triceps was elminated by extirpation of the inferior cervical sympathetic ganglion. The somatic supply was cut off by division of both roots of the sixth, seventh and eighth cervical nerves within the vertebral canal.