Neuron theory

Of all the cells, the nerve cells seem most complex, and of all the organs and systems of organs, the brain and nervous system seem most complex. Moreover, of all the parts of a human body, the brain and nervous system are, or should be, the most interesting, since it is they that make us human. Waldeyer-Hartz (see 1888) was the first to maintain that the nervous system was built out of separate cells and their delicate extensions. The delicate extensions, he pointed out, approached each other closely but did not actually meet, much less join, so that the nerve cells remained separate. He called the nerve cells neurons, and his thesis that the nervous system is composed of separate neurons is the neuron theory. An Italian histologist, Camillo Golgi (1843 or 1844–1926), fifteen years before, had devised a system of staining with silver compounds that brought out the structure of neurons in fine detail. Using this stain he could demonstrate that Waldeyer-Hartz’s views were correct. He could show that fine processes did indeed issue from the neurons and that those from one neuron approached but did not touch those of neighboring neurons. The tiny gaps between one neuron and the next are called synapses (oddly enough, from a Greek word meaning “union,” which they appeared to be at a casual glance but were not in actuality). A Spanish histologist, Santiago Ramón y Cajal (1852–1934), improved on Golgi’s stain, and by 1889 had worked out the cellular structure of the brain and spinal cord in detail, firmly establishing the neuron theory. For their work on the neuron theory, Golgi and Ramón y Cajal shared the Nobel Prize in medicine and physiology in 1906.