Effect of Anoxemia,Carbon Dioxide and Lactic Acid on the Autonomic Fibers of Somatic and Visceral Nerves

Abstract

In a previous paper, 1 the effects of anoxemia, CO₂ and lactic acid on certain fibers of somatic nerves were described. Further investigations by the author 2 and by Heinbecker and Bishop 3 have identified in autonomic nerves 2 other components of potential which possess properties different from those previously described by Gasser and Erlanger. 4 Similar action potentials traced by Erlanger and Gasser 5 from sympathetic rami into somatic nerves and thoroughly studied there by them apparently arise from similar fibers. We have found their potentials to have the same properties there as in autonomic nerves. These fibers have a higher threshold, a slower conduction rate, a longer absolutely and relatively refractory period, a longer chronaxie, and a potential at the stimulus of longer duration.

With the use of higher amplification (200 mm. per mv.) than employed in the previous work on CO₂, the compound conducted action potential of sciatic nerves of the frog, turtle, cat, dog and the monkey give rise to the same 4 components of potentials, named A, B₁, B₂ and C as are found in autonomic nerves. Taking the frog's sciatic as a type, the A wave arises from thickly myelinated fibers (somatic motor and sensory) as previously shown by Erlanger. 6 The B₁ wave presumed to correspond to the Delta wave described by Erlanger and Gasser but now with higher amplification no longer recognized by them as a separate entity is considered by the author, both because of its conduction rate and its other properties, to correspond to the B₁ wave described by the author 7 and by Bishop and Heinbecker. 4 In autonomic nerves it has been shown to arise from larger relatively thinly myelinated visceral afferent fibers.