Growth patterns of the peripheral axons of the spiral neurons in culture Free

Segments of the organ of Corti with its innervation preserved were excised from the newborn mouse and studied in culture. The following growth patterns were observed: (a) maintenance of the normal innervation pattern and growth along normal lines if the hair cells remain in their usual location, (2) growth by elongation of the fiber if the hair cells migrate into the out‐growth zone and if the fiber remains in contact with the receptor, and (3) free growth of the fiber if its connections with the hair cells are broken. Growth by elongation is confined to the area of hair cell displacement. The growth is well organized and the length of the fiber compensates strictly for the distance the respective hair cell has migrated. Free growth proceeds at a faster rate then does growth by elongation, is independent of the receptors, is unrestricted in length, and uncontrolled in amount. The growth is disorganized and luxuriant for at least several weeks after explanation. [Work supported by NIH grants NS08626 and NS12732.]