Cajal, Golgi, Nansen, Schäfer and the neuron doctrine.

The Nobel Prize for Physiology or Medicine of 1906 was shared by the Italian Camillo Golgi and the Spaniard Santiago Ramón y Cajal for their contributions to the knowledge of the micro-anatomy of the central nervous system. In his Nobel Lecture, Golgi defended the going-out-of-favour Reticular Theory, which stated that the nerve cells--or neurons--are fused together to form a diffuse network. Reticularists like Golgi insisted that the axons physically join one nerve cell to another. In contrast, Cajal in his lecture said that his own studies confirmed the observations of others that the neurons are independent of one another, a fact which is the anatomical basis of the now-accepted Neuron Doctrine (Theory). This much is well documented. Less well known, however, is the fact that evidence against the Reticular Theory had been mounting for some time prior to the Nobel Lecture. The Norwegian Fridtjof Nansen had reported in 1887 that, in his studies of the primitive creatures he studied in the sea near Bergen, he found no connections between the processes of the ganglion cells in their nervous systems. Nor is it adequately appreciated that ten years earlier, in 1877, the Englishman Edward Schäfer had similarly described seeing no connections between the nerve elements in the mantles of the jellyfish. This paper begins by charting the research that led directly to the awarding of the 1906 Nobel Prize. It then shows that long before the ultimate vindication of the Neuron Doctrine, researchers in several countries had been accumulating evidence that undermined or contradicted the Reticular Theory.