ABSTRACT
The mandibular portion of cranial nerve V of the teleost fish, Astronotus ocellatus, was totally severed and allowed to regenerate into its distal nervestump in a series of ten cases.
In a second series of fourteen cases, the two nerve branches supplying the elevator and depressor muscles of the mandible were sectioned separately and the nerve of the depressor muscles was crossed into the levator muscles and vice versa.
In both series, return of function in the re-innervated muscles was first detected about 8 days after nerve-section, and full recovery was achieved by the 18th to 21st day save for two exceptions in Series II in which the surgical crossunion proved faulty.
The recovered mandibular action was properly timed and co-ordinated from the beginning with the mandibular muscles of the opposite side.
It is inferred (a) that the regenerating motor-fibres establish functional connexions with foreign mandibular muscles, (b) that the muscles induce a local muscle specificity in the regenerated motor axons, and (c) that this ‘myotypic’ specificity determines in some way not yet analysed the central timing of motoneuron discharge in the trigeminal motor nucleus.
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