After doing well at school, Ramón y Cajal was apprenticed to a barber, then to a shoemaker, and lastly followed his father (at the latter’s insistence) in studying medicine. He began to practise in 1873, and then served in the army in Cuba. From 1884 he was a professor in Spain, at Madrid from 1892–1922. He was often unwell, having contracted malaria in Cuba and then tuberculosis in Spain. About 1885 he was shown a microscope section of brain tissue, stained with silver by Golgi’s method. He was fascinated by it, and proceeded to improve the method. Within a few years he had added greatly to knowledge of the nervous system, and his work on it filled the rest of his life. Ramón y Cajal worked on the connections of the cells in the brain and spinal cord and showed the great complexity of the system. The human brain contains about 1011 nerve cells (neurons), each connected with many others, giving a very large number of junction points (synapses). In opposition to Golgi, he argued that the nervous system consisted only of discrete nerve cells and their processes, with the axons ending in the grey matter of the brain, and not joining other axons or the cell bodies of other nerve cells (the neuron theory). He worked also on the difficult problem of the degeneration and regeneration of nerve cells, on the neuroglia, and on the retina. He shared a Nobel Prize with Golgi in 1906.