Jorge Francisco Tello Muñoz (1880–1958): First Pupil and the Man of Relay of Cajal

Santiago, Cajal's grandson, has said: “Tello was the first pupil (disciple) of Cajal, his most loyal coworker, his person of relay. They built a deep mutual respect and inalterable friendship, between master and pupil, that lasted until the day of death of the master in 1934” (Ramón y Cajal Junquera, 2005). The relationship between Tello and Cajal was not easy at the beginning. Cajal believed that Tello had copied in the examination for the prize of his university degree and wanted to exclude Tello from the competition. Fortunately, Dr. Olóriz, Professor of Internal Medicine, who was also member of the tribunal, convinced Cajal that this was impossible because he (Olóriz) had been sitting close to Tello during the whole time of the exam, and besides this, he was very confident on the capacity and honesty of the candidate. Tello, during the studies of the Medicine, worked as an intern in surgery with the famous Professor Ribera, and when he got his M.D. degree, he wanted to become a specialist in surgery. But Tello did not apply on time for the post of medical intern in surgery and, due to financial reasons, he decided to apply for an intern position in the laboratory of histology directed by Cajal, the only internship that was still available. Therefore, Cajal received Tello in his laboratory coldly and mistrustful. Nevertheless, very soon, Cajal completely changed his feeling for Tello. One morning, Cajal arrived at the laboratory and saw, astonished, some cages containing lizards that he had not ordered. Then, he asked to the concierge who answered that the animals had been ordered and paid by Mr. Tello. This agreeably impressed Cajal, who called Tello and asked him what he wanted to study in these animals. In his research on these reptiles, Tello discovered giant neurofibrils in the neurons of the spinal cord during winter lethargy. For the histological staining, Tello used the reduced silver nitrate method, recently invented by Cajal. This discovery was the starting point for Tello to further study the effects of physiological winter lethargy in neurons, phenomenon that he finally defined very well. The neurofibrils are protoplasmic organelles that are very sensible to changes in temperature. Due to the action of cold and heat, neurofibrils undergo transient morphologic conglutination and disjoining; in both cases, reversible when temperature backs to control conditions. Cajal himself and several other researchers confirmed these observations posteriorly. Cajal recognized the importance of Tello's discovery and ordered to publish a “preliminary note” in the second volume of the journal Trabajos del Laboratorio de Investigaciones Biológicas, as well as to publish the complete description later, in the third volume (Tello, 1904a). Then Cajal asked Tello to investigate the structure of the “corpus geniculatum externum” (Fig. 1) and the pupil, under the direction of the master, obtained several original findings (Tello, 1904b). As a result, Tello received the doctorate degree as well as, afterward, the “Extraordinary Prize” (30 June 1903). After the doctoral dissertation, Tello kept on working in Cajal's laboratory of neurohistology. He investigated the degenerative and regenerative processes in nerve endings (Tello, 1923a, 1942), motor plates, neuromuscular spindles of the skeletal muscles (Tello, 1907a, 1907b), the regenerative processes in the optic tracts (Tello, 1907a, 1907b, 1911a, 1911b), and the influence of neurotropism in the nervous centers (Tello, 1911b; Fig. 2). With his important findings, Tello came in support of Cajal's “Neurotropic Theory” (Tello, 1911b); not in vain, Dr. Francisco Tello chose the title “Actual ideas about Neurotropism” for his dissertation to be accepted as a member of the Royal National Academy of Medicine (Spain) in 1923 (Tello, 1923b). However, these findings will need more than 50 years to reach the international recognition that undoubtedly deserved and that deserve today. The Uruguayan researcher Alberto Aguayo, Director of Neurosciences researches at the McGill University (Montreal, Canada) reproduced the experiments by Tello in the early 1980s (Vikhansky, 2001), while the Italian Rita Levi Montalcini was awarded the 1986 Nobel Prize in Physiology or Medicine for discovering the first molecule known to stimulate the growth of nerves (NGF)—shared with Stanley Cohen (Vikhansky, 2001). Since long time before, Cajal was worried about the poor level of some disciplines, like Pathology and Bacteriology, in Spain. The talent, dedication, and work capacity of Tello determined Cajal to select him among all his pupils, and sent him to the most prestigious centers in Berlin (Germany) for both, Pathology and Bacteriology. In 1911, Tello worked with Prof. Von Benda at the Hospital Moabit, and with Johannes Orth at the Charité Hospital. He completed his stage abroad working at the Institute for Infectious Diseases “Robert Koch,” especially in the section for Epidemiology, under the supervision of Dr. Lentz. Once back in Madrid, Cajal created the Autopsy Department, within the Department of Pathology of the University of Madrid, nominating Tello as Chief Prosector. There was where Francisco Tello started performing autopsies and teaching Pathology, getting that all patients who died at the University Hospital of San Carlos were autopsied. Tello trained several physicians in this specialty and created the first school of Pathology in Spain. Once Cajal retired, Tello became Chairman of the Department of Histology and Pathology of the University of Madrid, and five of his pupils became Full Professors of Pathology: Fernando de Castro, Ramón Martínez Pérez, Juan Miguel Herrera Bollo, Julián Sanz-Ibáñez, and José Luis Arteta. Related to Bacteriology, Cajal, who was the Director of the “Hygiene Institute Alfonso XIII,” appointed Tello as Chief of the Section of Epidemiology. Here, Tello organized a course in Bacteriology, similar to the systematic course that he had attended in 1911 at the Robert Koch Institute, giving rise to a school of pupils in this discipline. At the same time, Tello kept on working in the afternoons at the “Laboratorio de Investigaciones Biológicas” (the original name of the laboratory of Cajal). In these years, Tello oriented his research in the Development of the Nervous System, toward the study of Neuroembryology. In this subject, the most relevant contributions by Tello were on the embryology of the cerebellum (Tello, 1940–41; Fig. 3). In the book The Cerebellum, Elwin wrote in the chapters of proprioceptors: “The embryology of the cerebellum is in the main account of the recent comprehensive work of Francisco Tello”. Tello also published important papers on development, evolution, and connections of the “corpus mamilaris” (Tello, 1936–37), among them, one published in the prestigious journal Zeitschrift für Mikroskopisch Anatomie Forschung, in the volume dedicated to Jan Boecke. I have previously referred the loyalty of Tello in following the indications and suggestions by Cajal. But I want now to emphasize the mutual recognition that had Cajal for Tello. In his answering speech to the dissertation of Tello to join the Royal National Academy of Medicine, Cajal stated: “the achievements of Tello, demonstrating in his experimental investigations that the CNS has regenerative capacity if adequately stimulated, it is an experimental feat which nobody never has reached before” (10). Cajal chose Tello as his successor at the Direction of the “Instituto de Higiene Alfoso XII,” as well as at the Direction of the “Instituto Cajal” (name received by former “Laboratorio de Investigaciones Biológicas” in 1920). Both, Cajal and Tello, coauthored one textbook on histology and micrography (“Elementos de Histología Normal y de técnica micrográfica”), and other one on pathology (“Manual Técnico de Anatomía Patológica”), published in 1918 (modified as “Manual de Anatomía Patológica General” in 1927). The professional relationship between Cajal and Tello was that of master–pupil and, short time afterward, that of tight collaborators. On the personal side, Santiago Ramón y Cajal considered Francisco Tello almost as his putative son. Tello had lost his mother when he was just four years old, and his father when he was 15 and, in my opinion, Cajal exercised on my grandfather a very important spiritual and moral influence. For Cajal, Tello was a son who inherited all his positions without having asked for them at all, and with whom he reached to have the greatest confidence. Finally, Cajal designated Tello as his testamentary executor. I want to thank the Instituto Cajal (Madrid, Spain) for its disposition and help in the elaboration of this manuscript.

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