52 Scientific American, April 2022
Cajal Institute, Cajal Legacy, Spanish National Research Council (CSIC), Madrid, Spain (
all images
)
H
our after hour, year after year, Santiago ramón y Cajal Sat
alone in his home laboratory, head bowed and back hunched, his
black eyes staring down the barrel of a microscope, the sole object
tethering him to the outside world. His wide forehead and aqui-
line nose gave him the look of a distinguished, almost regal, gen-
tleman, although the crown of his head was as bald as a monk’s.
He had only a crowd of glass bottles for an audience, some short
and stout, some tall and thin, stopped with cork and filled with white powders and colored liquids;
the other chairs, piled high with journals and textbooks, left no room for anyone else to sit. Stained
with dye, ink and blood, the tablecloth was strewn with drawings of forms at once otherworldly and
natural. Colorful transparent slides, mounted with slivers of nervous tissue from sacrificed animals
still gummy to the touch from chemical treatments, lay scattered on the worktable.
With his left thumb and forefinger, Cajal adjusted the corners
of the slide as if it were a miniature picture frame under the lens
of his microscope. With his right hand, he turned the brass knob
on the side of the instrument, muttering to himself as he drew the
image into focus: brownish-black bodies resembling inkblots and
radiating threadlike appendages set against a transparent yellow
background. The wondrous landscape of the brain was finally
revealed to him, more real than he could have ever imagined.
In the late 19th century most scientists believed the brain was
composed of a continuous tangle of fibers as serpentine as a laby-
rinth. Cajal produced the first clear evidence that the brain is
composed of individual cells, later termed neurons, that are fun-
damentally the same as those that make up the rest of the living
world. He believed that neurons served as storage units for men-
tal impressions such as thoughts and sensations, which com-
bined to form our experience of being alive: “To know the brain
is equivalent to ascertaining the material course of thought and
will,” he wrote. The highest ideal for a biologist, he declared, is
to clarify the enigma of the self. In the structure of neurons, Cajal
thought he had found the home of consciousness itself.
Cajal is considered the founder of modern neuroscience. His-
torians have ranked him alongside Darwin and Pasteur as one of
the greatest biologists of the 19th century and among Copernicus,
Galileo and Newton as one of the greatest scientists of all time. His
masterpiece, Texture of the Nervous System of Man and the Verte-
brates, is a foundational text for neuroscience, comparable to
On the Origin of Species for evolutionary biology. Cajal was
awarded the Nobel Prize in 1906 for his work on the structure of
neurons, whose birth, growth, decline and death he studied with
devotion and even a kind of compassion, almost as though they
were human beings. “The mysterious butterflies of the soul,” Cajal
Benjamin Ehrlich is author of The Dreams of Santiago
Ramón y Cajal, the first English translation of Cajal’s dream
journals. His work has appeared in the New England Review,
Nautilus and the Paris Review Daily. His new book is The
Brain in Search of Itself (Farrar, Straus and Giroux, 2022).
A YOUNG CAJAL appears in an 1871 photographic portrait.
