Paolo Mazzarello graduated from medical school with honors from the University of Pavia, Italy, and earned a PhD in neurological sciences from the University of Milan. He has since been a researcher for the National Research Council at the Institute of Molecular Genetics in Pavia, Italy and is currently Professor of History of Medicine at the University of Pavia, Italy. His most recent book, Golgi: A Biography of the Founder of Modern Neuroscience, looks at an extraordinary intellectual who explored three major fields of biology and medicine, namely neuroscience, emerging cell biology, and the new science of medical microbiology. In the excerpt below we learn a little bit about Golgi’s key discovery, the black reaction.
One winter day at the end of 1872, or the beginning of 1873, a scientist sat down to work at his microscope in the unlikely setting of an asylum for lunatics in northern Italy, after focusing back and forth for a while…
What a fantastic sight! On a yellow, completely transparent background, there appear sparsely scattered black fibers, smooth and small or thick and prickly, as well as black, triangular, star- or rod-shaped bodies! Just like fine India ink drawings on transparent Japanese paper. The scientist gazes upon it in astonishment. He is more accustomed to the chaotic images produced by carminic acid and hematoxylin, which yield one dubious interpretation after another. Here, on the other hand, everything is absolutely clear, without any possibility of confusion. There is nothing more to interpret; one need only observe and note these cells, with their different, ramified extensions, like plants in the morning frost, covering an astonishingly large space in wavy lines; thse smooth and uniform extensions which, springing from the cell, cover great distances, before suddenly splitting up into a bunch of innumerable fibers…The delighted and astonished gaze cannot tear itself away from this fantastic sight. Methodic wishful thinking has become reality. Metal impregnation has produced a magnificent and unexpected slide.
This is how the renowned Spanish histologist Santiago Ramón y Cajal imagined the scene that, on that day, must have presented itself to the eyes of Camillo Golgi, the young chief physician of the Pie Case degli Incurabili (Charitable Home for Incurables) of Abbiategrasso. This was the moment of the discovery of the “reazione nera” (black reaction), a revolutionary method for studying the structure of the nervous system. This discovery contributed, more than thirty years later, to the awarding of the Nobel Prize for Medicine to Golgi.
For every student of medicine or biology, the name Golgi is synonymous with one of the basic structures in the cell: the Golgi Apparatus or Golgi Complex. But this is only one of the many discoveries and achievements, particularly in the neurosciences, for which Golgi’s name deserves to be known by a much wider public than just devotees of biomedical sciences. Unfortunately, his scientific fame lags far behind the historical significance of his discoveries. The historical-critical literature on Golgi is scanty and the appraisal of his scientific work has been negatively affected by his rejection of the theory of the neuron and by the erroneous idea that his discovery of the black reaction was the result of pure chance.
The theory of the neuron, which was definitively confirmed only after the advent of the electron microscope, is an important example of a revolutionary conceptual transformation in biology. Using the terminology of Thomas S. Kuhn, without necessarily adopting his ideas on the evolution of scientific thought, the theory of the neuron represents a fundamental “paradigm” of the neurosciences in the same sense that atomic-molecular interpretation of matter or the theory of the discrete transmission of hereditary characteristics constitute fundamental paradigms of chemistry and genetics, respectively. This concept of the neuron (and particularly that of synapses), by virtue of its being the elemental unit of modulation and transmission of information, has also assumed a preeminent role in many disciplines associated with the neurosciences such as informatics and artificial intelligence. The multidisciplinary significance of the theory of the neuron does not simply represent an automatic extension to the nervous system of the principles of cellular theory, just as quantum mechanics is not simply a consequences of applying classical mechanics to subatomic structures. Given the biophysical characteristics of neurons, the laws of their reciprocal communication, the complexity of their connections, and the extraordinary nature of the activities to which they give rise, it is evident how this theory constitutes the basis of a new segment of the scientific research that integrates “polyphonically” contributions from physics, electrochemistry, informatics, and clinical medicine, and in addition classical physiology and anatomy-histology. From this perspective, the theory must be considered one of the great intellectual conquests of the nineteenth century.
To the end of his life Gogli remained a fiery opponent of this theory, despite having contributed materially its formulation, as he recognized explicitly in his Nobel Prize acceptance speech. The technical histological revolution that he developed, the black reaction (known also as Golgi’s Method or chrome-silver reaction), which allowed the detailed investigation of the morphology of neurons and the basic architecture of cerebral tissue, was in fact the fundamental prerequisite that made possible the “paradigmatic” generalization of the theory of the neuron.
Often in the history of biology (and even more so in scientific discoveries generally), the introduction of a new technique revolutionizes a whole area of research, radically transforming preexisting disciplines and creating others from scratch. One is reminded of the effect that monoclonal antibodies had on immunology and other branches of biology, or of the impact that the technology of recombinant DNA had on genetics. The black reaction represented, for the histology of the nervous system, a breakthrough of comparable importance, permitting the development of neuroanatomy as an autonomous discipline, and thus contributing to the birth of modern neuroscience. Only after the introduction of Golgi’s Method, and the extraordinary structural descriptions of the nervous tissues obtained with it, did morphological investigations begin to be connected to physiological and functional investigations…