Santiago Ramón y Cajal

RAMÓN Y CAJAL Santiago (Santiago Ramón y Cajal, born 1852), Spanish histologist and researcher of the nervous system. In 1873 he graduated from the medical faculty in Zaragoza and began working as a military doctor. In 1883 he was appointed to the chair of comparative anatomy in Valencia, in 1887 he moved to Barcelona as professor of histology, and in 1892 to Madrid. Cajal's main merit lies in the field of studying the nervous system. He studies both the external forms and the internal structure of nerve cells, nerve endings, the connection between cells, phylo- and ontogenesis, degeneration and regeneration of nerve tissue, and neuroglia.

An orthodox cellularist, opponent of reticulists (i.e., those who recognize the syncytial structure of tissue), Cajal is the founder of the neuron theory. According to Cajal, nerve cells and neuroglial cells are separate organisms with mobile processes. Contact is established between nerve cells—neurons. Excitation is perceived by the dendrites and the cell body and transmitted along the axon—the principle of dynamic polarization; later he corrects this and speaks of axopetal polarization. In matters of the development of the nervous system, he puts forward a number of propositions; for example, in vertebrates there are two nervous systems: sensory and cortico-cerebral. Individual improvement is based on the strengthening and growth of connections between the nerve cells of the brain. Nerve regeneration proceeds exclusively through the growth of central segments and their collaterals, rather than autogenously from Schwann cells. During the growth of a cell process, there is an initial "chaotic" period when the process emits a series of seemingly trial branches, most of which perish. He explains the neurotropism of nerve fibers by enzymes that activate protoplasmic assimilation and originate from embryonic connective tissue or Schwann cells. Original is the idea that neurofibrils of a nerve cell are living formations: the smallest neurobionts, connecting in chains, form colonies, as it were—fibrils. Of great value are Cajal's investigations in synaptology, i.e., the doctrine of connections between neurons in the most diverse areas of the brain, especially in the cerebral cortex. Neuroglia consists of individual cells separated from embryonic ependymal cells; there are no glial fibrils outside the cells (contrary to Weigert's view). Cajal initially divided neuroglia cells into protoplasmic and fibrous astrocytes and a third element; later, together with his students (del Río Hortega), he began to distinguish cells of mesodermal origin in the basis of the brain—mesoglia. Cajal's scientific works. In addition to numerous articles, manuals on normal and pathological histology, and manuals on technique, Ramón y Cajal authored the following monographs: «Les idées nouvelles sur la fine anatomie des centres nerveux» (P., 1894); «Studien über die Hirnrinde des Menschen» (Hefte 1-5, Lpz., 1900); «Die Retina der Wirbeltiere» (Berlin, 1894); «Studien über Nervenregeneration» (Lpz., 1908); «Histologie du système nerveux de l'homme et des vertébrés» (vol. I-II, P., 1909-1911); «Estudios sobre la degeneración y regeneración del sistema nervioso» (vol. I-II, Madrid, 1913-1914); «Étude sur la neurogénèse de quelque vertébrés» (P., 1923); «Degeneration and regeneration of the nervous system» (L., 1928). In addition, he published «Revista trimestral micrográfica» (vol. I-V, Madrid, 1896-1900) and published «Trabajos del Laboratorio de investigaciones biológicas» (Madrid, since 1901).