Abstract

The essay introduces how Paul A. Weiss (1898-1989) analyzed his data on neuronal outgrowth and axonal transport, supported by constriction experiments of thousands of living mature nerve fibers. At the University of Chicago his group measured the steady proximo-distal flow of nerve fibers. To visualize the data he used tissue culturing, light microscopy, radioactive tracers, time-lapse motion pictures and electronmicroscopy. The work resulted in the discovery of fasciculation of outgrowing nerves and a computation of the rate of axonal transport, published in a classical article in 1948. He stated that the outgrowth of nerve fibers occurs from nerve centers in their nucleated cell bodies by fasciculation and protein synthesis. However, at that time one suspected the published microphotograph to be an idealized image and, therefore, did not accept the analysis, or the 'new' knowledge. In the mid 1960s the improved technique of autoradiography confirmed in an indirect way Weiss' data and analysis of axonal transport. The objective here is to show (1) how Weiss employed the visibility of micrographs and drawings to corroborate his observations and analysis on axonal dynamics, and (2) to offer some tentative suggestions why his colleagues did not accept the 'neuro-images' as an evidence of new knowledge