Nicholas J. WADE¹ and Marco PICCOLINO^2
1Department of Psychology, University of Dundee, Dundee, Scotland.  n.j.wade AT dundee.ac.uk
²Dipartimento di Biologia, Università di Ferrara, Italy.  pic AT dns.unife.it

Camillo Golgi’s silver staining procedure (resulting in a black reaction – reazione nera) for nerve fibres, published in 1873, was used to good effect in the study of the visual pathways.  First in 1887, Golgi’s student, Ferruccio Tartuferi, presented beautiful diagrams of retinal structure, with its vertical and horizontal connections. In the same year, Santiago Ramón y Cajal learned about Golgi’s staining technique and soon after applied it to the retina.  Where Tartuferi’s representation emphasised the lateral connections of the horizontal and amacrine cells, Cajal’s positted more importance to the verticalorganisation of receptor, bipolar and retinal ganglion cell connections.  This reflected the differences in the conceptions of the nervous system adopted by Golgi and Cajal (reticular and neuronal, respectively).  Cajal took the dissimilarity between the rods and cones to support duplicity theory.  He also sought to retain the distinction for the fibers in connection with the receptors.  The presence of lateral connections from the horizontal and amacrine cells presented a problem for Cajal’s conception of the manner in which vision operated, and he tended to exclude these two classes of cells from the operative visual network of the retina. The principle of point to point projection featured strongly in Cajal’s analysis of vision and it is also a fundamental feature of photography, with which he was involved for much of his life.  It is mainly due to his study of retinal architecture (culminating in 1893 with his monumental memoir La rétine des vertébrés), that the projective model dominated physiological investigations of the retina for the first half of the 20th century.  Thus, the functional paradigm of retinal and visual physiology adopted by Cajal was clearly inspired to the process of photography. Not only did he develop great skills as a photographer but he also applied them to stereoscopic vision: he devised a technique not unlike the principle of random dot stereograms, with the intention of encrypting messages.  Modern conceptions of retinal function perhaps owe more to Golgi’s network model than to Cajal’s point projection principle.

Pavia, Italy, 2006