Cajal

“In only a few years of searching [in Barcelona, from 1887 on], Cajal had concluded that the nervous system is composed of units: a cell body with dendrites that receive incoming information and propel the nervous impulse down a single departing axon to stimulate the next cell. Finally, he deduced that since there is no continuity of substance between neurons, the electrical impulse between cells must be transmitted by an unknown chemical induction effect. . . . Cajal’s ideas incorporated all that is now felt to be fundamentally true about the basic structure and function of the nervous system. At that time, however, the matter was both imperfectly understood and hotly contested” (Rapport, 104-105, 120-121). Cajal “was modifying not only Golgi’s staining method [via his “double impregnation” staining method (99-100)] but also his theories of neural conduction” (118). . . .[Using embryonic tissue, where myelin is scant and nerve paths less cluttered (101)] “He had seen that axons end, by this time in the cerebellum, and later in the retina and the olfactory bulb. Those endings invariably conformed to the shape of the dendrites of the next cell. There was no fibril of connection. There was a gap” (121). Utilizing only the light microscope, unable actually to see the synaptic cleft in the manner that electron microscopy permitted, Cajal “was correct in his basic description of neuronal anatomy, dynamic polarization, and synaptic transmission” (180).