Any way, he wrote a book - "Reglas y consejos sobre investigacion cientifica" translated as "Advice for a Young Investigator" - to help budding scientists through their first years as researchers. While some of his advice is dated, such as the section on how to choose a wife, most is well worth the $14. What follows is a brief summary and some comments on the 1999 MIT Press pocket edition (with one of the worst quality bindings in modern history), translated by Swanson and Swanson (who have done a good job).
There is a Foreword by Larry W. Swanson with a short biography of Dr. Cajal and some suggested readings from his quite large production. Then there are three prefaces, for each of the second, third and fourth editions.
There are nine chapters, each addressing a different potential difficulty.
The introduction concerns itself with which theory of science a scientist should build his understanding of nature upon. The answer is determinism. Cajal is very clear that a scientist should not spend his time delving too deeply into the various theories of knowledge and science. He writes:
"...by abandoning the ethereal realm of philosophical principles and abstract methods we can descend to the solid ground of experimental science..."In this he comes quite close to my own thoughts on the matter (which may be why I like the book in the first place). Today, pure determinism is still usefully utilized in Chaos Theory, or the study of non-linear dynamics, but in general the focus today should be on statistical determinism. That is, the fact that we cannot know the full state of any system (at least any interesting system) induces variation and that this punches a quite large hole in classical determinism, but can be compensated for by studying larger populations and using statistics. Actually Cajal does not mention statistics at all, probably because it was just starting out as a field at the time.
2. Beginner's Traps
In the second chapter Cajal goes through some things that might unduly discourage the beginning scientist from his chosen path. Basically that well known feeling that those who went before were smarter, saw farther and thought deeper than you ever could. He makes the case that it only seems so after the fact, and that with hard work and time a scientist starting out today will appear equally daunting to those starting out in the future.
3. Intellectual Qualities
Cajal's main point about the mind of the investigator is that it does not have to be exceedingly brilliant as long as it is tenacious and a bit vain. He does mention originality, but his focus really is on hard work and the striving for glory. These are qualities he dejectedly notes are none too present in his contemporary Spaniards, while he holds the Germans in high regard. He writes:
"In Spain, where laziness is a religion rather than a vice, there is little appreciation for how the ... work of German [scientists] is accomplished - espeially when it would appear that the time required ... might involve decades!"
Rather poignantly, the endnotes have been expanded with the editions. In relation to a section written in the original 1893 edition Cajal later notes:
"This frank optimism is now greatly undermined by the hideous international war that began in 1914... It is sad to admit, but all nations become ferociously imperialistic as soon as possible... So much for the weak and unpatriotic!"
4. What Newcomers to Biological Research Should Know
In this chapter Cajal handles the opposing needs for the investigator to know a lot about disparate fields, especially the basic sciences, and at the same time specialize as much as possible to be able to produce original work.
Perhaps his most important point is the short section on "Mastery of Technique", as he writes:
"...the most important scientific conquests have been won by only a dozen men who have become known for their invention of improvement of a research method..."
5. Diseases of the Will
This is clearly the most entertaining section. The six most dangerous personalities - "who never produce any original work and almost never write anything." - are described in detail. I will only quote the his classification, the rest you should read in his original, quite wonderful prose.
"These illustrious failures may be classified in the following way: the dilettantes of contemplators; the erudite or bibliophiles; the instrument addicts; the megalomaniacs; the misfits; and the theory builders."
While these are quite fun, and you can always find some colleague that fits each personality, the more important lesson is that everyone gets trapped in these mires of the mind from time to time. The important thing is to realise that you are stuck in an unproductive mindset and be able to move on.
6. Social Factors Beneficial to Scientific Work
These are the ever current problems of funding, combining a profession with science and combining work and family. His basic stance is that you can always do science, but you should be ready to sacrifice having a life. Good advice.
7. Stages of Scientific Research
Here Cajal goes over the practicalities of the experimental method. Observation - Experimentation - Working hypotheses - and Proof. It is material gone over many times in other books, although Cajal has the benefit of being brief.
8. On Writing Scientific Papers
To start with Cajal references a Mr. Billings and states four rules: Have something to say; Say it; and Stop once it is said. The fourth rule wasn't as catchy so I'll just drop it. Then he writes a bit about credit and curtesy.
9. The Investigator as Teacher
The final chapter expounds on the importance of fostering future researchers to continue the work once you have gone. He concedes that it might be restful and rewarding to work in solitude but that "Posterity has always been generous with the founders of schools." He then goes on to describe the pains and pleasures of trying to combine research and teaching. First, how to find a suitable potential investigator; then how to guide him; and finally how to see him
become a successful scientist leave science for profit and glory.
In conclusion, it is one of the few books that actually describes what it means to be a scientist, specifically a physiologist. It is certainly one of the very, very few that does so while being well written. I heartily recommend it to all my colleagues, and to any one else who might be interested in what science really is.