Observations, chiefly by the degeneration method, on possible efferent fibres in the dorsal nerve‐roots of the toad and frog

TLDR: The presumption being that any departure from the Bell-Magendie law of the conduction of impulses will be associated with a corresponding exception to the Wallerian law of degeneration, the degeneration method has been given most attention.

Abstract: EXPERIMENTS made with the object of determining whether efferent fibres exist in the dorsal spinal nerve-roots of the frog have given contradictory results in the hands of different observers. On the one hand Steinach (1) finds that spinal nerves send viscero-motor fibres to the cesophagus, stomach and intestine solely by the dorsal roots, and to the rectum and bladder in part by the dorsal roots. On the other hand, Horton-Smith (2) found no evidence for the presence of viscero-motor fibres in the dorsal roots: but in a small percentage of cases he found that motor fibres to certain skeletal muscles were contained in the 7th, 8th or 9th dorsal root of one side. Wana (8), working under Steinach, has been able to observe this effect on skeletal muscles, though the number of cases in which it occurred was relatively smaller than in Horton-Smith's experiments. The above observations were all made by the method of stimulation, and it seemed better to attack the question by another method of experiment than simply to add to the tale of conflicting evidence. The presumption being that any departure from the Bell-Magendie law of the conduction of impulses will be associated with a corresponding exception to the Wallerian law of degeneration, I have given most attention to the degeneration method, though some experiments have also been made by the old method of stimulation. The results on certain points seem to be decisive, but I have been unable, for lack of time, to carry out the observations as fully as I had hoped.