December 2021 Newsletter Robert Hooke and Santiago Ramón y Cajal: two geniuses united by the cell

Dr Tomás Camacho

Vigo (Spain)


Considering his accomplishments, it is a surprise that Robert Hooke is not more renowned. As a physician, I especially esteem him as the person who identified biology’s most essential unit, the cell. Like Leonardo da Vinci, Hooke excelled in an incredible array of fields. Robert Hooke was a true Renaissance man: the remarkable range of his achievements throughout the 1600s encompassed pneumatics, microscopy, mechanics, astronomy and even civil engineering and architecture. Definitely, Hooke was the greatest inventor and designer of scientific instruments of the 17th century. Yet this “English Leonardo” –wellknown in his time– slipped into relative obscurity for several centuries. He was primarily an experimentalist, convinced that the limitations of the human senses could be overcome with powerful and sensitive instruments. He was not only an exceptional inventor and mechanic but he firmly believed in the importance of data, experimentation and observation in the face of philosophical talk.

Hooke would have gone down in the history of Science for any of his many inventions but in the field of Biology he is fundamentally remembered as the discoverer of the cell. In his work "Micrographia or some physiological descriptions of minute bodies made by magnifying glasses" (1665), Hooke details 60 objects observed using his compound microscope. Among many other observations, Hooke made fine cuts in cork blocks, observing the existence in this material of a honeycomb-shaped structure that he called "cells"

(or cells or cells). It is evident that Hooke's term to refer to these cavities was substantially different from the current concept, since Hooke did not conceive these cells as constituent units of living beings, for which it would have to wait almost two hundred more years, but the cell had been baptized and names allow concepts to emerge. What was missing was what it was like, how it worked and where it came from, but that is another story. 

The discovery of the cell was the essential first step in understanding the microscopic organization of the brain. Without this, we would not have been able to know the structure and function of the different types of cells in the nervous system: neurons and glial cells; Nor would we have been able to interpret the parts of nerve cells as axons, dendrites or neuronal cells, much less understand subcellular structures such as synapses, receptors, transmitters, channels and all the myriad structures to which Hooke's microscope opened the door for us, to which the concept of cell gave meaning. Without the discovery of what we might call microscopic neuroscience, our knowledge of the brain would have remained a field of speculation. When it was possible to see that the nervous system contained nerve cells, capable of receiving and emitting signals, capable of integrating information, capable of modifying their functioning due to the effects of learning, injury or drug use, to give a few examples, we were able to to understand the structural substratum of all mental functions and of "diseases of the soul." The vital spirits were losing the battle because the cell was observable, measurable and understandable, and they were not.

In 1682, Robert Hooke read a lecture to the Royal Society of London, in which he described a mechanistic model of human memory.  The lecture is remarkable because it represents one of the earliest and most comprehensive attempts to construct a mechanistic model of a cognitive process, yet it is virtually unknown among psychologists today. The lecture addressed questions of encoding, memory capacity, repetition, retrieval, and forgetting-some of these in a surprisingly modern way (The posthumous Works fo Robert Hooke. “An hypothetical explication of memory; how the organs made use of by the mind in its operations may be mechanically understood”).

From 1695, Hooke's health deteriorated, suffering from swollen legs, chest pains, dizziness, emaciation, blindness,… These symptoms suggest cardiovascular disease and diabetes. He died without a will on March 3, 1703 in London. One of his friends wrote "the old philosopher has finally left, to experiment with his ancestors." Hooke was originally buried in St. Helen’s Church, Bishopsgate but his remains were moved in the 19th century and the final location of his burial has been lost, an ungrateful fate for an exceptional man.

Cajal is considered the father of modern neuroscience, as important in his field as Charles Darwin or Louis Pasteur are in theirs. His discoveries, made during the last dozen years of the 19th-century, concern the way neurons, the building blocks of the brain, spinal cord and nervous system, communicate with one another. His theory — immediately accepted by most, but not strictly proven until the 1950s — was that neurons are in touch without touching. They communicate across infinitesimal gaps known as synaptic clefts. Through a chemical and electrical transmission, the single-stemmed axon of one neuron talks to the branched root-like dendrite of another. This process of synaptic messaging between unconnected cells came to be called the Neuron Doctrine, and in 1906, it earned Cajal the Nobel Prize in Physiology or Medicine. He shared it with the Italian histologist Camillo Golgi.

From the 19th of November, 2020 through the 5th of December 2021, the National Museum of Natural Sciences, Madrid, Spain will be hosting an exhibition featuring Cajal's scientific drawings, photographs, scientific equipment and personal objects from the Legado Cajal, Instituto Cajal, Madrid, Spain. In the same museum there is another exhibition: Microbiology: exploring beyond the visible, a fascinating sample of microbiology. In this exhibition is an original Leeuwenhoek microscope, from 1680, and the original edition of Robert Hooke's "Micrographia" (1665), both belonging to the Camacho & Pallas collection.