I. Croonian Lecture .—Observations on isolated nerve (with particular reference to carbon dioxide)

As was pointed out ten years ago by Wedenski, from telephone observations of the negative variation, by Waller, from galvanometric observations of the same, and by Bowditch from the observation of long-persisting excitability in the nerves of temporarily curarised mammals, nerve is now admitted to be practically inexhaustible. The apparent exhaustion of nerve when a nerve-muscle preparation is submitted to prolonged excitation is, as was first demonstrated in Bernstein’s experiment, not an exhaustion of nerve, but an exhaustion of the organ of intermediation between nerve and muscle, which, as pointed out by Waller, is the weak link in the neuro-muscular chain, being the point at which functional failure is first manifested, in fatigue, in nerve degeneration, in intoxication by curare (Bernard), and at death. Taking as the sign of action artificially excited in a nerve, the negative variation of its current of rest (du Bois-Reymond) or current of injury (Hermann), the long endurance by nerve of excitation excessive in strength and in length, is well shown by prolonged photographic records of the galvanometric indications, which exhibit little or no decline, in marked contrast with similar records of the negative variation of muscle which declinespari passu with the declining contraction due to fatigue of the motor end plates. This steady regularity of response renders nerve pre-eminently suitable to the systematic study of its experimental disturbance.