The Man Who Drew Neurons – Loretta G. Breuning Ph.D. – Advice for a Young Investigator – Santiago Ramón y Cajal.

There is every reason to believe that when the human intellect ignores reality and concentrates within, it can no longer explain the simplest inner workings of life’s machinery or of the world around us.

By abandoning the ethereal realm of philosophical principles and abstract methods we can descend to the solid ground of experimental science, as well as to the sphere of ethical considerations involved in the process of inquiry. In taking this course, simple, genuinely useful advice for the novice can be found.

Cajal had discovered the synapse and with fundamental insight went on to describe the organization of all the major neural systems in terms of chains of independent neurons and the concept of functional polarity unidirectional information flow in circuits.

The man who discovered the synapse, Santiago Ramón y Cajal also wrote a book of career advice. “Advice for a Young Investigator”

He made huge contributions to our knowledge of the brain. He discovered that neurons transmit electricity in only one direction. He wrote a textbook on the nervous system, based on his own extensive lab work and sketches, that was used to train doctors for generations.

I wanted career advice from this person.

So why does the same advice need to be repeated every generation?

Because it conflicts with our natural impulses.

Natural selection built a brain that makes careful decisions about where to invest its energy. It doesn’t like to waste effort on failed endeavors. A lion would starve to death if it kept running after gazelles that got away. This makes it hard to persist when we run into setbacks.

The brain we’ve inherited seeks safety in numbers. A gazelle that wandered off would soon be eaten alive. Thus our brain alarms us with a bad feeling when we’re isolated. This makes it hard to trust your judgment when the rest of the herd walks away.

Our brain is designed to weigh risk and reward, but it defines them with neural pathways built from the risks and rewards of your past. New information has trouble getting in unless we invest our full attention. This leaves us with less energy for other things, so we often just stick to our old risk/reward pathways.

Psychology Today

Santiago Ramón y Cajal (1852-1934) was a Spanish neuroscientist and pathologist, specializing in neuroanatomy, particularly the histology of the central nervous system. He and Camillo Golgi received the Nobel Prize in Physiology or Medicine in 1906, with Ramón y Cajal thereby becoming the first person of Spanish origin who won a scientific Nobel Prize.

His original investigations of the microscopic structure of the brain made him a pioneer of modern neuroscience. Hundreds of his drawings illustrating the delicate arborizations of brain cells are still in use for educational and training purposes.

Advice for a Young Investigator (1897)

Santiago Ramón y Cajal


Santiago Ramon y Cajal (1852-1934) is one of the more fascinating personalities in science. Above all he was the most important neuroanatomist since Andreas Vesalius, the Renaissance founder of modern biology. However, Cajal was also a thoughtful and inspired teacher, he made several lasting contributions to Spanish literature (his autobiography, a popular book of aphorisms, and reflections on old age), and he wrote one of the early books on the theory and practice of color photography. Furthermore, he was an exceptional artist, perhaps the best ever to draw the circuits of the brain, which he could never photograph to his satisfaction.

In his early thirties, Cajal wrote and illustrated the first original textbook of histology in Spain, which remained a standard throughout his lifetime.

The first draft of his unique book of practical, fatherly advice to young people in the early stages of their research careers was begun soon after moving to the chair of histology and pathological anatomy at the University of Madrid about a decade later, when he also wrote the first major review of his investigations with Camillo Golgi’s silver chromate method: New Ideas on the Structure of the Nervous System (1894).

This succinct book redefined how brain circuits had been described. In it, Cajal presented histological evidence that the central nervous system is not a syncytium or reticulum of cells as commonly believed at the time. Instead, it consists of individual neurons that usually conduct information in just one direction. The information output of the neuron is down a single axon and its branches to terminal boutons that end on or near the input side of another neuron (its cell body and dendrites). Cajal had discovered the synapse and with fundamental insight went on to describe the organization of all the major neural systems in terms of chains of independent neurons and the concept of functional polarity (unidirectional information flow in circuits). He was the first to explain in modern terms the organization of reflex and voluntary control pathways to the motor system, and this conceptual advance was the structural foundation of Sir Charles Sherrington’s modern physiological explanation of reflexes and their control.

By the time the Advice for a Young Investigator was finally published, he was beginning to synthesize the vast research that established his reputation in a three volume masterpiece, the Histology of the Nervous System in Man and Vertebrates (1899-1904). So the Advice became a popular vehicle for Cajal to write down the thoughts and anecdotes he would give to students and colleagues about how to make important original contributions in any branch of science, and it was so successful that the third edition is still in print (in Spanish).

Part of the Advice is based on an analysis of his own success, while the rest comes from a judicious selection of wisdom from other places and other people’s lives. Nevertheless, it is obviously Cajal’s analysis of his own scientific career. As such, it is deeply embedded in contemporary Spanish culture and in the childhood of a country doctor’s son. Hard work, ambition, patience, humility, seriousness, and passion for work, family, and country were among the traits he considered essential. But above all, master technique and produce original data; all the rest will follow.

It is interesting to compare Cajal the writer and Cajal the scientist. As a distinguished author of advice, autobiography, and reflections on life, he displayed a complex mixture of the romantic, idealist, patriot, and realist. And a sense of humor is obvious in his delightful chapter here on diseases of the will, where stereotypes of eccentric scientists are diagnosed according to symptoms we have all seen, and their prognosis discussed. In stark contrast, his scientific publications are almost ruthlessly systematic, descriptive, and deductive. He once wrote that his account of nervous system structure was not based on the appearance of a nerve cell here and there, but on the analysis of millions of neurons.

Because Cajal revealed so much about his thoughts and feelings in the Advice and in his autobiography, Reflections on My Life, it is easy to see his genius as well as his flaws. He deals with many broad issues of morals, religion, and patriotism that are often avoided, invariably generate controversy, and go in and out of fashion. However, it is important to bear in mind that he was writing in the late nineteenth century to aspiring researchers in his native Spain, which at the time was not one of the scientifically and politically elite countries of Europe. Thus, some of his advice may now appear dated or irrelevant to young people in North America and Europe who enjoy relative peace, prosperity, and intellectual security. However, it may become relevant to them sometime in the future, and it still applies to many other cultures.

This translation is based on two sources, the fourth edition of Reglas y Consejos sobre Investigacion Biologica (Ios tonicos de la voluntad) (1916), and an English translation of the sixth edition by J.Ma. Sanchez-Perez, which was edited and annotated by C.B. Courville as Precepts and Counsels in Scientific Investigation. Stimulants of the Spirit (1951).

We had originally thought that it would be worthwhile simply to reprint the Sanchez-Perez and Courville work, but finally decided that the translation was too literal, and in some few cases inaccurate, for today’s students. Our goal has been to write a modern rather than literal translation, retaining as much flavor of the original as we could.

The fourth edition was published when Cajal was over sixty, and was never substantially revised again. The later Spanish editions have two chapters at the end that are concerned primarily with conditions in Spain at the time, and they have not been translated because of their limited relevance today. We thank Graciela Sanchez-Watts for help with translating certain difficult passages.

Larry W. Swanson Los Angeles, February 1, 1998

1 Introduction

Thoughts about general methods. Abstract rules are sterile. Need to enlighten the mind and strengthen resolve. Organization of the book.

I shall assume that the reader’s general education and background in philosophy are sufficient to understand that the major sources of knowledge include observation, experiment, and reasoning by induction and deduction.

Instead of elaborating on accepted principles, let us simply point out that for the last hundred years the natural sciences have abandoned completely the Aristotelian principles of intuition, inspiration, and dogmatism.

The unique method of reflection indulged in by the Pythagoreans and followers of Plato (and pursued in modern times by Descartes, Fichte, Krause, Hegel, and more recently at least partly by Bergson) involves exploring one’s own mind or soul to discover universal laws and solutions to the great secrets of life. Today this approach can only generate feelings of sorrow and compassion, the latter because of talent wasted in the pursuit of chimeras, and the former because of all the time and work so pitifully squandered.

The history of civilization proves beyond doubt just how sterile the repeated attempts of metaphysics to guess at nature’s laws have been. Instead, there is every reason to believe that when the human intellect ignores reality and concentrates within, it can no longer explain the simplest inner workings of life’s machinery or of the world around us.

The intellect is presented with phenomena marching in review before the sensory organs. It can be truly useful and productive only when limiting itself to the modest tasks of observation, description, and comparison, and of classification that is based on analogies and differences. A knowledge of underlying causes and empirical laws will then come slowly through the use of inductive methods.

Another commonplace worth repeating is that science cannot hope to solve Ultimate Causes. In other words, science can never understand the foundation hidden below the appearance of phenomena in the universe. As Claude Bernard has pointed out, researchers cannot transcend the determinism of phenomena; instead, their mission is limited to demonstrating the how, never the why, of observed changes.

This is a modest goal in the eyes of philosophy, yet an imposing challenge in actual practice. Knowing the conditions under which a phenomenon occurs allows us to reproduce or eliminate it at will, therefore allowing us to control and use it for the benefit of humanity. Foresight and action are the advantages we obtain from a deterministic view of phenomena.

The severe constraints imposed by determinism may appear to limit philosophy in a rather arbitrary way. However, there is no denying that in the natural sciences, and especially in biology, it is a very effective tool for avoiding the innate tendency to explain the universe as a whole in terms of general laws. They are like a germ with all the necessary parts, just as a seed contains all the potentialities of the future tree within it. Now and then philosophers invade the field of biological sciences with these beguiling generalizations, which tend to be unproductive, purely verbal solutions lacking in substance. At best, they may prove useful when viewed simply as working hypotheses.

Thus, we are forced to concede that the ”great enigmas” of the universe listed by Du Bois-Raymond are beyond our understanding at the present time. The great German physiologist pointed out that we must resign ourselves to the state of ignoramus, or even the inexorable ignorabimus.

There is no doubt that the human mind is fundamentally incapable of solving these formidable problems (the origin of life, nature of matter, origin of movement, and appearance of consciousness). Our brain is an organ of action that is directed toward practical tasks; it does not appear to have been built for discovering the ultimate causes of things, but rather for determining their immediate causes and invariant relationships. And whereas this may appear to be very little, it is in fact a great deal. Having been granted the immense advantage of participating in the unfolding of our world, and of modifying it to life’s advantage, we may proceed quite nicely without knowing the essence of things.

It would not be wise in discussing general principles of research to overlook those panaceas of scientific method so highly recommended by Claude Bernard, which are to be found in Bacon’s Novum Organum and Descartes’s Book of Methods. They are exceptionally good at stimulating thought, but are much less effective in teaching one how to discover. After confessing that reading them may suggest a fruitful idea or two, I must further confess an inclination to share De Maistre’s view of the Novum Organum: ”Those who have made the greatest discoveries in science never read it, and Bacon himself failed to make a single discovery based on his own rules.”

Liebig appears even more harsh in his celebrated Academic Discourse when he states that Bacon was a scientific dilettante whose writings contain nothing of the processes leading to discovery, regardless of inflated praise from jurists, historians, and others far removed from science.

No one fails to use instinctively the following general principles of Descartes when approaching any difficult problem: ”Do not acknowledge as true anything that is not obvious, divide a problem into as many parts as necessary to attack it in the best way, and start an analysis by examining the simplest and most easily understood parts before ascending gradually to an understanding of the most complex.” The merit of the French philosopher is not based on his application of these principles but rather on having formulated them clearly and rigorously after having profited by them unconsciously, like everyone else, in his thinking about philosophy and geometry.

I believe that the slight advantage gained from reading such work, and in general any work concerned with philosophical methods of investigation, is based on the vague, general nature of the rules they express. In other words, when they are not simply empty formulas they become formal expressions of the mechanism of understanding used during the process of research. This mechanism acts unconsciously in every well-organized and cultivated mind, and when the philosopher reflexly formulates psychological principles, neither the author nor the reader can improve their respective abilities for scientific investigation.

Those writing on logical methods impress me in the same way as would a speaker attempting to improve his eloquence by learning about brain speech centers, about voice mechanics, and about the distribution of nerves to the larynx, as if knowing these anatomical and physiological details would create organization where none exists, or refine what we already have.

It is important to note that the most brilliant discoveries have not relied on a formal knowledge of logic. Instead, their discoverers have had an acute inner logic that generates ideas with the same unstudied unconsciousness that allowed Jourdain to create prose. Reading the work of the great scientific pioneers such as Galileo, Kepler, Newton, Lavoisier, Geoffroy Saint-Hilaire, Faraday, Ampere, Bernard, Pasteur, Virchow, and Liebig is considerably more effective. However, it is important to realize that if we lack even a spark of the splendid light that shone in those minds, and at least a trace of the noble zeal that motivated such distinguished individuals, this exercise may if nothing else convert us to enthusiastic or insightful commentators on their work, perhaps even to good scientific writers, but it will not create the spirit of investigation within us.

A knowledge of principles governing the historical unfolding of science also provides no great advantage in understanding the process of research. Herbert Spencer proposed that intellectual progress emerges from that which is homogeneous and that which is heterogeneous, and by virtue of the instability of that which is homogeneous, and of the principle that every cause produces more than one effect, each discovery immediately stimulates many other discoveries. However, even if this concept allows us to appreciate the historical march of science, it cannot provide us with the key to its revelations. The important thing is to discover how each investigator, in his own special domain, was able to segregate heterogeneous from homogeneous, and to learn why many of those who set out to accomplish a particular goal did not succeed.

Let me assert without further ado that there are no rules of logic for making discoveries, let alone for converting those lacking a natural talent for thinking logically into successful researchers. As for geniuses, it is well known that they have difficulty bowing to rules, they prefer to make them instead. Condorcet has noted that ”The mediocre can be educated; geniuses educate themselves.”

Must we therefore abandon any attempt to instruct and educate about the process of scientific research? Shall we leave the beginner to his own devices, confused and abandoned, struggling without guidance or advice along a path strewn with difficulties and dangers?

Definitely not. In fact, just the opposite, we believe that by abandoning the ethereal realm of philosophical principles and abstract methods we can descend to the solid ground of experimental science, as well as to the sphere of ethical considerations involved in the process of inquiry. In taking this course, simple, genuinely useful advice for the novice can be found.

In my view, some advice about what should be known, about what technical education should be acquired, about the intense motivation needed to succeed, and about the carelessness and inclination toward bias that must be avoided, is far more useful than all the rules and warnings of theoretical logic. This is the justification for the present work, which contains those encouraging words and paternal admonitions that the writer would have liked so much to receive at the beginning of his own modest scientific career.

My remarks will not be of much value to those having had the good fortune to receive an education in the laboratory of a distinguished scientist, under the beneficial influence of living rules embodied in a learned personality who is inspired by the noble vocation of science combined with teaching. They will also be of little use to those energetic individuals, those gifted souls mentioned above, who obviously need only the guidance provided by study and reflection to gain an understanding of the truth. Nevertheless, it is perhaps worth repeating that they may prove comforting and useful to the large number of modest individuals with a retiring nature who, despite yearning for reputation, have not yet reaped the desired harvest, due either to a certain lack of determination or to misdirected efforts.

This advice is aimed more at the spirit than the intellect because I am convinced, and Payot wisely agrees, that the former is as amenable to education as the latter. Furthermore, I believe that all outstanding work, in art as well as in science, results from immense zeal applied to a great idea.

The present work is divided into nine chapters. In the second I will try to show how the prejudices and lax judgment that weaken the novice can be avoided. These problems destroy the self-confidence needed for any investigation to reach a happy conclusion. In the third chapter I will consider the moral values that should be displayed, which are like stimulants of the will. In the fourth Chapter I will suggest what needs to be known in preparing for a competent struggle with nature. In the fifth, I will point out certain impairments of the will and of judgment that must be avoided. In the sixth, I will discuss social conditions that favor scientific work, as well as influences of the family circle. In the seventh, I will outline how to plan and carry out the investigation itself (based on observation, explanation or hypothesis, and proof). In the eighth I will deal with how to write scientific papers; and finally, in the ninth Chapter the investigator’s moral obligations as a teacher will be considered.


Advice for a Young Investigator

by Santiago Ramón y Cayal

get it at


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