Santiago Ramón y Cajal

Shared the 1906 Nobel Prize in Physiology or Medicine with Camillo Golgi for work on the structure of the nervous system. In his own Nobel lecture, Golgi set out his disagreement with Cajal's view of how nerve cells connect.

From 1888 he argued that nerve cells are separate units that communicate by contact rather than forming a continuous network. By 1891 he had also proposed that impulses travel in one direction through each cell, from the dendrites and cell body to the axon.

Between 1889 and 1913 he developed several staining methods and variants, including the reduced silver nitrate method of 1903. About 4,500 slides from his collection and almost 2,000 scientific drawings, nearly all by his own hand, survive at the Cajal Institute in Madrid.

In October 1889 Cajal travelled to the German Anatomical Society's congress in Berlin with his own slides and microscope. Arthur van Gehuchten, who was there, later recalled that he stood almost alone amid sceptical smiles until he took Albert von Kölliker aside to a microscope. Within months Kölliker had published confirmations of his findings.

Choosing to show his preparations to the leading sceptics in person, instead of waiting for his papers to be read, is consistent with a strong habit of taking the initiative. Proactive Agency

Around 1918-20 his pupil Pío del Río Hortega found that cells Cajal had described as lacking processes did in fact have them. By Río Hortega's own account, Cajal called the conclusions too daring and did not encourage publication. When the findings were later confirmed, Cajal's memoirs credited the discovery to another pupil.

This account comes from the pupil concerned and sits alongside other episodes in which Cajal did revise his views, which is one reason his profile places him near the middle on changing his mind. Belief Updating

In 1887 the neurologist Luis Simarro showed Cajal brain sections stained with Golgi's silver method, a technique Cajal had dismissed after reading about it. He adopted it at once and applied it to young animals and embryos, whose nerve fibres are easier to stain. His first major findings followed in 1888.

Taking up a method he had earlier set aside, and adapting it through his choice of material, offers one example of the hands-on trial and variation seen throughout his work. Experimentation