The Stimulation Threshold of Different Sympathetic Fibre Groups as Correlated to Their Functional Differentiation.

Summary. The differences in stimulation threshold of the preganglionic fibres to a number of functionally‐differentiated sympathetic neuro‐effectors have been studied. The results indicate that the fibres to the cutaneous arterio‐venous anastomoses, to the nictitating membrane and the pupil have as an average the lowest threshold, and hence probably the largest fibre diameters. Another group is formed by the constrictor fibres to, e. g ., the ordinary skin vessels, the muscle and the tongue vessels, while the sympathetic dilator fibres to the muscle vessels have by far the highest threshold, and therefore probably the smallest diameter.