The neuron doctrine is a concept formed during the turn of the twentieth century that describes the properties of neurons, the specialized cells that compose the nervous system. The neuron doctrine was one of two major theories on the composition of the nervous system at the time. Advocates of the neuron doctrine claimed that the nervous system was composed of discrete cellular units. Proponents of the alternative reticular theory, on the other hand, argued that the entire nervous system was a continuous network of cells, without gaps or synapses between the cells. In 1873, physician and reticular theory supporter Camillo Golgi developed a staining technique called the black reaction, a neuron staining technique that allowed for complete visibility of nerve cells, which enabled scientists to view a complete neuron cell and its cellular structures. Later, neuroscientist Santiago Ramón y Cajal used the black reaction to show the existence of synapses, or gaps between neurons, and argued that his evidence supported the neuron doctrine. The confirmation of the neuron doctrine showed that neurons function as discrete and independent cells, not as a single network, within the nervous system.