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(1) Following the injection of l-[¹⁴C]proline into one eye in carp, the label appeared in the contralateral optic nerve via axoplasmic flow. As reported previously, protein-bound activity showed faster and slower axoplasmic transport. Labeled free proline appeared in nerve before labeled protein and thus did not originate from labeled protein.

(2) When [¹⁴C]α-aminoisobutyric acid, l-proline, or d-glutamic acid was injected into the eye, the label in the nerve decreased in a distal direction. The radioactivity gave two peaks of maximal activity with time in the whole nerve and in nerve sections, indicating a faster and a slower component of the axoplasmic transport of amino acids. There were no peaks of activity in the nerve on the control side. Estimated transport rates for the fast components were 90–110 mm/day; values for the slow component varied between 5 and 20 mm/day. The acid-soluble activity did not reach the …