[In the following excerpt, Stevenson offers a brief summary of Ramón y Cajal's life and his Nobel Prize-winning research in neurophysiology.]

Santiago Ramón y Cajal was born May 1, 1852, In Petilla, an isolated village in the Spanish Pyrenees, where his father was "surgeon of the second class." The elder Ramón later extended his studies and in time became professor of anatomy at Zaragoza. The son's unfortunate early schooling, under tyrannical teachers, failed to reveal his gifts. It was followed by apprenticeship, first to a barber, then to a shoemaker. His father then undertook to teach him, particularly in osteology, which revealed the boy's talent as a draftsman. Thereafter he studied medicine at Zaragoza and was graduated in 1873. Then came compulsory service in the Spanish army, chiefly in Cuba, until 1875; during this interval he suffered severely from malaria and dysentery. After taking a medical degree at Madrid, he became a demonstrator and then, in 1877, professor of anatomy at Zaragoza; but he was soon forced to interrupt his work because of pulmonary tuberculosis. He married in 1879 and in 1884 was called to the chair of anatomy at Valencia. For a time he worked at bacteriology and serology, but turned to his proper field, histology, and in 1887 was given a chair in that subject at Barcelona. Learning of the Golgi silver stain from Luis Simarra, a neuropsychiatrist of Madrid, Ramón y Cajal developed an improvement of his own which he began to use in the study of the nervous system. This was the first of his several important innovations in staining technique. In 1889 he demonstrated his work before the German Society of Anatomists, was praised by Kölliker, and was soon acclaimed by German histologists generally. In 1892 he was appointed professor of normal histology and pathologic anatomy at Madrid. International honors now accumulated. There followed many years of intensive labor. By 1923 he had already published 237 scientific papers. He also wrote a large number of books, including not only comprehensive works on the nervous system but popular essays, a treatise on color photography, etc. He died on October 18, 1934, at the age of eighty-two.

From the sum of my researches springs a general concept which comprehends the following propositions:

The nerve cells are morphologic units, the neurons, to use the word sanctioned by the authority of Professor Waldeyer. This had already been demonstrated, as regards the dendritic or protoplasmic extensions of the nerve cells, by my illustrious colleague Professor Golgi; but when our researches began there were only conjectures more or less tenable regarding the way in which the ultimate divisions of the axons and nerve collaterals are arranged. Our observations, with Golgi's method, which we applied first in the cerebellum, then in the spinal marrow, the brain, the olfactory bulb, the optic lobe, the retina, etc. of embryos and young animals, revealed, in my opinion, the terminal disposition of the nerve fibers. These, in their ramifications to several junctures, incline constantly toward the neuronal body and toward the protoplasmic expansions, around which arise plexuses, or nerve nests, very close-woven and very rich. The ... . morphologic dispositions, which vary in form according to the nerve centers one studies, attest that the nerve elements have reciprocal relations of contiguity and not of continuity, and that communications, more or less intimate, are always established not only between the nervous arborizations but between the ramifications of one part and the body and protoplasmic extensions of another part. . . .

These facts, recognized in all the nerve centers with the aid of two very different methods (Golgi's and Ehrlich's) . . . involve three physiological postulates:

(1) Since nature, in order to assure and amplify contacts, has created complicated systems of ramifications around the cells (systems which would become incomprehensible by the hypothesis of continuity), it is necessary to admit that the nervous currents are transmitted from one element to another by virtue of a sort of induction, or influence at a distance.

(2) It is also necessary to suppose that the cellular bodies and the dendritic prolongations, like the axis cylinders, are induction apparatus, since they represent intermediate links between the afferent nerve fibers and the axons mentioned. This is what Bethe, Simarro, Donaggio, we ourselves, etc., have confirmed quite recently, in demonstrating, with the aid of neurofibrillary methods, a perfect structural concordance between the dendrites and the axis-cylinder prolongation.

(3) Examination of the transmission of nerve impulses in the sense organs, such as the retina, the olfactory bulb, the sensory ganglions and the spinal marrow, etc., show not only that the protoplasmic expansions play a conducting role but also that the movement of the nerve impulse in these prolongations is toward the cell body, whereas in the axons it is away from the cell body. This principle, called the dynamic polarization of neurons, formulated a long time ago by van Gehuchten and us as an induction drawn from numerous morphological facts, is not contrary to the new researches on the constitution of nerve protoplasm. In fact we shall see that the framework of neurofibrils makes up a continuous reticulum from the dendrites and the cell body to the axon and its peripheral termination.

[Translated from Santiago Ramón y Cajal, "Structure et Connexions des Neurones," Les Prix Nobel en 1906.]

The quotation from Ramón y Cajal has been selected as the latter's attempt at a general summation of an important part of his work. The neuron theory, here presented in a condensed form, was firmly established by his researches. Its importance to subsequent investigators can hardly be assessed in a few words. It underlies the exceedingly important work of Sir Charles Sherrington. It guided the thought of Egas Moniz, who introduced prefrontal leucotomy (see below, pp. 264-270). It is one of the basic theories of modern biological science.

Ramón y Cajal's contributions are also too numerous and too complex for summary treatment. As he himself said, "Unfortunately it is absolutely impossible to condense in a few pages morphological facts the description of which occupies a large number of brochures with hundreds of drawings." It may be mentioned, however, that another Nobel laureate, Robert Bárány . . . , in attempting to connect the function of the labyrinth apparatus of the ear with cerebellar function, was initially dependent on the Spanish histologist's account of the nerve connections involved. It is safe to say that there is no neurologist or neuroanatomist of recent times who does not owe him a similar debt.

Even more lasting than his wealth of recorded observations will be the improved methods of Cajal and his disciples. First, in 1888, he increased the applicability of the Golgi stain. In 1903 he developed his own reduced silver nitrate strain. .. . In 1913 he introduced the gold sublimate stain. . . . His eminent pupils Achucarro and Hortega [introduced] the silver carbonate stains. . . .

These methods in the hands of Cajal and his students have clarified much of the embryology of each cellular element in the nervous system. Furthermore, the finer details of gliomas revealed by these stains, with the accumulating light from embryology, have given the neurosurgeon useful correlations of structure and biologic characteristics of brain tumors. [Wilbur Sprong, "Santiago Ramón y Cajal: 1852-1934," Archives of Neurology and Psychiatry, Vol. 33 (1935), pp. 156-162.]

REFERENCES

Cannon, Dorothy F. Explorer of the Human Brain: The Life of Santiago Ramón y Cajal (1852-1934) (New York: Schuman, 1949).

Ramón y Cajal, Santiago. Recollections of My Life, translated by E. Home Craigie and Juan Cano (Philadelphia: American Philosophical Society, 1937), 2 vols.

Sprong, Wilbur. "Santiago Ramón y Cajal: 1852-1934," Archives of Neurology and Psychiatry, Vol. 33 (1935), pp. 156-162.