Soon he became an assistant in the School of Anatomy in the Faculty of Medicine at Zaragoza (1875); later, at his own request, Director of the Zaragoza Museum (1879). In 1877 Santigo was awarded the degree of Doctor of Medicine at Madrid. In 1883 Santiago became Professor of Descriptive and General Anatomy at Valencia, where (in recognition of his service during a cholera epidemic, the Privencial Government of Zaragoza awarded him a modern Zeiss microscope). In 1887, Santiago was appointed Professor of Histology and Pathological Anatomy at Barcelona. This was the year when Santiago started using Golgi's silver nitrate staining. Nerve cells appeared "brownish black even to thier finiest branchlets ... against a transparent yelllow backgrund ... sharp as a sketch with Chinese ink".

In 1892, Santiago was appointed to the Chair of Histology and Pathological Anatomy at Madrid. In 1900-1901 he became Director of the "Instituto Nacional de Higiene" and of the "Investigaciones Biológicas".

In 1880 Santiago began to publish scientific works, including Manual de Histología normal y Té'cnica micrográfica (Manual of normal histology and micrographic technique), 1889 (2nd ed., 1893); Les nouvelles id%eacute;es sur la fine anatomie des centres nerveux (New ideas on the fine anatomy of the nerve centres), 1894; Textura del sistema nervioso del hombre y de los vertebrados (Textbook on the nervous system of man and the vertebrates), 1897-1899; Die Retina der Wirbelthiere (The retina of vertebrates), 1894; also. more than 100 articles in French and Spanish scientific periodicals, especially on the fine structure of the nervous system, the brain and spinal cord, as well as muscles and other tissues, and various subjects in the field of general pathology.

Among the distinctions won by Cajal are the following: Member of the Royal Academy of Sciences of Madrid (1895); of the Royal Academy of Medicine of Madrid (1897); of the Spanish Society of Natural History and of the Academy of Sciences of Lisbon (1897); Honorary Member of the Spanish Medical and Surgical Academy and also of several other Spanish societies.

He was also made honorary Doctor of Medicine of the Universities of Cambridge (1894) and Würzburg (1896) and Doctor of Philosophy of the Clark University (Worcester, U.S.A., 1899).

Cajal was a corresponding member of several societies: the Physical-Medical Society of Würzburg (1895); the Medical Society of Berlin (1895); the Society of Medical Sciences of Lisbon (1896); the Vienna Society for Psychiatry and Neurology (1896); the Society of Biology of Paris (1887); the National Medical Academy of Lima (1897); Conimbricensis Instituti Societas (Coimbra, 1898); and Member of Honour of the Italian Psychiatric Society (1896) as well as of the Medical Society of Ghent (Belgium, 1900). In 1906 he was elected an Associate Member of the Academy of Medicine, Paris; in 1916 he became a member of the Swedish Academy of Sciences. Cajàl has been awarded several prizes, for example the Rubio Prize of 1,000 pesetas for his previously mentioned Elementos de Histología, etc., the Fauvelle Prize of 1,500 francs of the Society of Biology of Paris (1896); the Moscow Prize of 5,000 francs, established by the Congress of Moscow (1897) to reward medical works which, published during the latter three years, have rendered the greatest services to science and humanity was awarded to Ramon y Cajàl by the International Congress of Medicine in Paris (1900). In 1905, the Royal Academy of Sciences of Berlin awarded him the Helmholtz Medal. He shared the Nobel Prize for 1906 with Camillo Golgi for their work on the structure of the nervous system.

In 1952 a volume of 651 pages was published «In honour of Santiago Ramón y Cajal on the centenary of his birth (1852) by members of a research group in neurophysiology» at the Caroline Institute (Acta Physiol. Scand., Vol. 29, Suppl. 106).

In 1879 Cajal married Doña Silvería Fañanás García. They had four daughters and three sons.

Born in Spain, he did all his studies there and rose in stature to become Professor of Anatomy at Valencia, later histology in normal and pathologic histology at Barcelona and then to Madrid as Professor of normal histology and pathological anatomy. He and Camillo Golgi received the Nobel Prize in 1906 for introduction of the silver-chromate stain. Later he set out carefully to explore the finer aspects of the brain. With his reduced silver nitrate technique he demonstrated neurons and their connections so easily. His introduction of his gold chloride- mercury bichloride technique to demonstrate astrocytes was a monumental contribution as was his work on degeneration and regeneration of the nervous system later. He will be remembered as a world famous neuropathologist.

In 1879 he married Silvería Fañanás García, a non-educated young woman, who stood at his side for the rest of their lives (she died in 1930). They had seven children (two of them died in their childhood).

In Zaragoza, Cajal purchased in 1877 with his own funds ("using every peseta saved from the service in Cuba"), an old-fashioned microscope and started his scientific activity. His first studies were devoted to inflammation and to the structure of muscle fibers. In 1883, Cajal was appointed to the chair of Anatomy in Valencia. In 1885, during his tenure as Professor of the University of Valencia, the Provincial Government of Zaragoza, in recognition of his labor during a cholera epidemic, awarded him with a modern Zeiss microscope. At the end of 1887 Cajal moved to Barcelona, where he accepted the chair of Normal and Pathological Histology, and in 1892 he was appointed Professor of Histology and Pathological Anatomy at the University of Madrid. Cajal continued to work productively in Madrid until his death in 1934.

The key event for Cajal's scientific career and for the development of modern neuroscience took place in Madrid in 1887, when Cajal was 35 years old. In this year, Luis Simarro Lacabra, a brilliant psychiatrist interested in histological research, showed to Cajal, who had traveled from Valencia to get an update on technological advances, material impregnated with the Golgi staining. Dr. Simarro had just returned from Paris, and had brought specimens stained by the new technique of silver impregnation, that had been discovered 14 years earlier by Camillo Golgi but still had a very limited diffusion. Cajal wrote in his autobiography "it was there, in the house of Dr. Simarro...that for the first time I had an opportunity to admire...those famous sections of the brain impregnated by the silver method of the Savant of Pavia."

At the time, Cajal had only been studying the nervous system for one year, mainly to collect suitable illustrations for a book of histological techniques, and he had realized how inadequate the ordinary methods were to study the nervous tissue. The observation of preparations impregnated by the Golgi stain was a flash of lightning: "a look was enough" and Cajal was enraptured. Nerve cells appeared "coloured brownish black even to their finest branchlets, standing out with unsurpassable clarity upon a transparent yellow background. All was sharp as a sketch with Chinese ink," Cajal wrote in his autobiography. In a feverish burst of activity ("...as new facts appeared in my preparations, ideas boiled up and jostled each other in my mind. A fever for publication devoured me"), Cajal worked on the retina, the cerebellum and the spinal cord, applying to the tissue the Golgi stain, of which he worked out some modifications.

In October 1889, Cajal who had never traveled outside Spain except for his service in Cuba, went to Berlin, to the Congress of the German Anatomical Society, to show his slides to the leading authorities in the field, in order to convince them of the importance of his observations. On this occasion, he obtained the recognition of several qualified professors, including the eminent Swiss histologist Rudolf Albert von Kölliker (1817-1905), who from there on became a supporter of Cajal and of the "neuron doctrine," which would be officially enunciated by Wilhelm Waldeyer (1836-1921) in 1891.

Cajal was fiercely opposed to the idea that the nervous system was made up a network of continuous elements, as it had been stated by Joseph von Gerlach (1820-1896) and supported by Golgi himself. Camillo Golgi had believed to have found in his own preparations the demonstration that the nervous system was made of a widespread network of filaments in continuity one with the other (the rete nervosa diffusa, 'diffuse neural network'). On the contrary, since the first observations and in his subsequent studies, Cajal's imagination was fired by the idea that the nervous system is made up of billions of separate nerve cells. Cajal's work led to the conclusion that the basic units of the nervous system were represented by individual cellular elements (which Waldeyer christened as "neurons" in 1891). This conclusion is the modern basic principle of the organization of the nervous system.

Cajal’s opus "Textura del Sistema Nervioso del Hombre y los Vertebrados" (1894-1904), was made available to the international scientific community in its French translation, "Histologie du Système Nerveux de l’Homme et des Vertébrés", (translated by L. Azoulay, published in 1911 by Maloine, Paris; the English translation, by N. and L.W. Swanson, was published in 1994 by Oxford University Press). Cajal’s opus provided the foundation of modern neuroanatomy, with a detailed description of nerve cell organization in the central and peripheral nervous system of many different animal species, and was illustrated by Cajal’s renowned drawings, which for decades (and even nowadays) have been reproduced in neuroscience textbooks.

In addition, Cajal defined "the law of dynamic polarization," stating that the nerve cells are polarized, receiving information on their cell bodies and dendrites, and conducting information to distant locations through axons, which turned out to be a basic principle of the functioning of neural connections. Cajal also made fundamental observations on the development of the nervous system and its reaction to injuries (his volume "Degeneration and Regeneration of the Nervous System" translated and edited by R. M. May, London, Oxford University Press, 1928, has been re-edited by J. DeFelipe and E.G. Jones, Oxford University Press, 1991).

Golgi and Cajal, who shared the Nobel Prize in 1906 for their studies on the nervous system, met only in Stockholm, to receive the award. Golgi gave his Nobel lecture first, in which he tied to his belief in "reticular" neural networks, which was entirely contradicted by Cajal's Nobel lecture. Cajal, a strenuous supporter of the contiguity (and not the continuity) of individual cells representing the basic units of the nervous system, fought for his ideas until his death.

Golgi and Cajal certainly shared the same passion for science and dedication to science but their personalities were very different. Cajal, impetuous, burning with enthusiasm, dedicated his life to the study of the organization of the nervous system, on which he made fundamental discoveries with his peculiar talent and intuition. Golgi, a "cooler" academic, discovered the tool used by Cajal in his studies and provided outstanding contributions in many fields of cell biology and of pathology, and important contributions also on the structure of the nervous system (such, for example, the description of branches given off by the axon, of different types of neurons, of glial cells). However, Golgi misinterpreted the overall view of the structural organization of the nervous system, which instead has been worked