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Neuron doctrine
The neuron doctrine is the concept that the nervous system is made up of discrete individual cells, a discovery due to decisive neuro-anatomical work of Santiago Ramón y Cajal and later presented by, among others, H. Waldeyer-Hartz. The term ''neuron'' (spelled ''neurone'' in British English) was itself coined by Waldeyer as a way of identifying the cells in question. The ''neuron doctrine'', as it became known, served to position neurons as special cases under the broader cell theory evolved some decades earlier. He appropriated the concept not from his own research but from the disparate observation of the histological work of Albert von Kölliker, Camillo Golgi, Franz Nissl, Santiago Ramón y Cajal, Auguste Forel and others.
==Historical context==
Theodor Schwann proposed in 1839 that the tissues of all organisms are composed of cells. Schwann was expanding on the proposal of his good friend Matthias Jakob Schleiden the previous year that all plant tissues were composed of cells. The nervous system stood as an exception. Although nerve cells had been described in tissue by numerous investigators including Jan Purkinje, Gabriel Valentin, and Robert Remak, the relationship between the nerve cells and other features such as dendrites and axons was not clear. The connections between the large cell bodies and smaller features could not be observed, and it was possible that neurofibrils would stand as an exception to cell theory as non-cellular components of living tissue. Technical limitations of microscopy and tissue preparation were largely responsible. Chromatic aberration, spherical aberration and the dependence on natural light all played a role in limiting microscope performance in the early 19th century. Tissue was typically lightly mashed in water and pressed between a glass slide and cover slip. There was also a limited number of dyes and fixatives available prior to the middle of the 19th century.
A landmark development came from Camillo Golgi who invented a silver staining technique in 1873 which he called ''la reazione nera'' (black reaction), but more popularly known as Golgi stain or Golgi method, in his honour. Using this technique nerve cells with their highly branched dendrites and axon could be clearly visualised against a yellow background. Unfortunately Golgi described the nervous system as a continuous single network, in support of a notion called reticular theory. It was reasonable at the time because under light microscope the nerve cells are merely a mesh of single thread. Santiago Ramón y Cajal started investigating nervous system in 1887 using Golgi stain. In the first issue of the ''Revista Trimestral de Histología Normal y Patológica'' (May, 1888) Cajal reported that the nerve cells were not continuous in the brain of birds. Cajal's discovery was the decisive evidence for the discontinuity of nervous system and the presence of large number of individual nerve cells. Golgi and Cajal were jointly awarded the 1906 Nobel Prize for Physiology or Medicine, that resulted in a lasting conflicting ideas and controversies between the two scientists. The matter was finally resolved in 1950s with the development of electron microscopy by which it was unambiguously demonstrated that nerve cells were individual cells interconnected through synapses to form a nervous system, thereby validating the neuron theory.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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