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. 2019 Feb 18:13:3.
doi: 10.3389/fnana.2019.00003. eCollection 2019.

The Original Histological Slides of Camillo Golgi and His Discoveries on Neuronal Structure

Marina Bentivoglio  1   2 , Tiziana Cotrufo  1 , Sergio Ferrari  1 , Chiara Tesoriero  1 , Sara Mariotto  1 , Giuseppe Bertini  1 , Antonella Berzero  3 , Paolo Mazzarello  3   4
Affiliations

The Original Histological Slides of Camillo Golgi and His Discoveries on Neuronal Structure

Marina Bentivoglio et al. Front Neuroanat. .

Abstract

The metallic impregnation invented by Camillo Golgi in 1873 has allowed the visualization of individual neurons in their entirety, leading to a breakthrough in the knowledge on the structure of the nervous system. Professor of Histology and of General Pathology, Golgi worked for decades at the University of Pavia, leading a very active laboratory. Unfortunately, most of Golgi's histological preparations are lost. The present contribution provides an account of the original slides on the nervous system from Golgi's laboratory available nowadays at the Golgi Museum and Historical Museum of the University of Pavia. Knowledge on the organization of the nervous tissue at the time of Golgi's observations is recalled. Notes on the equipment of Golgi's laboratory and the methodology Golgi used for his preparations are presented. Images of neurons from his slides (mostly from hippocampus, neocortex and cerebellum) are here shown for the first time together with some of Golgi's drawings. The sections are stained with the Golgi impregnation and Cajal stain. Golgi-impregnated sections are very thick (some more than 150 μm) and require continuous focusing during the microscopic observation. Heterogeneity of neuronal size and shape, free endings of distal dendritic arborizations, axonal branching stand out at the microscopic observation of Golgi-impregnated sections and in Golgi's drawings, and were novel findings at his time. Golgi also pointed out that the axon only originates from cell bodies, representing a constant and distinctive feature of nerve cells which distinguishes them from glia, and subserving transmission at a distance. Dendritic spines can be seen in some cortical neurons, although Golgi, possibly worried about artifacts, did not identify them. The puzzling intricacy of fully impregnated nervous tissue components offered to the first microscopic observations still elicit nowadays the emotion Golgi must have felt looking at his slides.

Keywords: Golgi staining; Purkinje cells; axon collaterals; cerebral cortex; dendritic spines; hippocampus; history of neuroscience.

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Figures

Figure 1
Figure 1
Camillo Golgi at his laboratory bench in the Institute of General Pathology of the University of Pavia around 1920. Reproduced with permission of the University Museum System of Pavia.
Figure 2
Figure 2
(A) Drawing from Deiters (1865) of an “isolated ganglion cell from the gray matter of the spinal cord… a, the main axis cylinder extension, b,b,b, the fine axis cylinder extensions coming from the protoplasmic extensions.” (translation in Shepherd, 2016). (B,C) Drawings by Dogiel (1891) illustrating a reticular dendritic interconnection (“protoplasmic net”). in the retina; the axons are in red.
Figure 3
Figure 3
Photographs of some of the slides. The labels in (A,B) are signed by Golgi with the indication of the year 1899; (C) shows an example of a wooden slide; the label in (D) has the indication “Cajal”; the label in (E) has a comment signed by Dominick Purpura in 1973 (see text).
Figure 4
Figure 4
Equipment of the laboratory of Camillo Golgi in the years that followed his appointment as Professor of Histology at the University of Pavia in 1876, when Golgi's studies focused on the nervous system. The equipment is on display at the Golgi museum (Berzero et al., 2018). (A) Microtome by the German anatomist and physiologist Gustav Fritsch (1838–1927), bought in 1878. (B) Microtome by the French histologist and anatomist Louis Ranvier (1835–1922) to cut by hand, with the razor shown in the figure, sections sufficiently thin for microscopic examination from tissue blocks fixed to the cylinder; this microtome was bought in 1879. (C) Hartnack-Prazmowski microscope, bought in 1877 from the firm Hartnack had established in Paris in partnership with the Polish mathematician and astronomer Adam Prazmowski (1821–1885). (D) Microscope by Edmund Hartnack (1826–1891), renowned German microscope maker, bought in 1876.
Figure 5
Figure 5
Drawing (A) and images (B,C) from Golgi-impregnated pes Hippocampi major (Ammon's horn) of the rabbit. (A) The drawing is Plate XIII from Golgi (1885), the translation of the original figure legend is provided by Bentivoglio and Swanson in Golgi et al. (2001). In the figure legend, Golgi noted the “different shapes presented by these cells.” The initial part of the “nerve process” (the axon) is drawn in red, and Golgi noted in the legend that “it should be considered a general rule that this part ramifies into numerous secondary fibrils that branch profusely.” (B,C) Impregnated neurons in Golgi's slides, showing what he should have seen. Scale bars: 200 μm in (B), 50 μm in (C).
Figure 6
Figure 6
Drawing (A) and images (B–D) from a Golgi-impregnated “vertical section” through the pes Hippocampi major (Ammon's horn) of the rabbit. (A) The drawing is Plate XXI from Golgi (1885), and, as for Figure 5, the translation is provided by Bentivoglio and Swanson in Golgi et al. (2001). In the figure legend Golgi described a “ventricular epithelium,” composed by cells “strikingly analogous to. neuroglial cells,” a “convoluted gray layer,” and “small nerve cells of the fascia dentata.” (B–D) Images from a Golgi's slide. Scale bars: 200 μm in (B), 30 μm in (C), 50 μm in (D).
Figure 7
Figure 7
Drawing (A) and images (B) of Golgi-impregnated neurons of the cerebral cortex. (A) The drawing is Plate I from Golgi (1885). In the legend Golgi stated that the plate, illustrating “some types of ganglion cells in the cerebral cortex,” is especially destined to show the origin and branching of the axon (“the only nervous prolongation of each ganglion cell”); the cells are from the frontal (“anterior central”; cells 1, 2, 4, 5, 9, 10) and occipital (cells 3, 6–8) human cerebral cortex. The legend states that, on the basis of their axonal ramifications, cells 1 and 3 illustrate examples of the first type of neurons (currently named as “Golgi type I,” see text) and cell 2 an example of the second type (currently “Golgi type II”). The legend also states that the axon could not be followed because it became too thin “destined to get lost in the diffuse net.” Scale bar in (B): 30 μm.
Figure 8
Figure 8
Golgi-impregnated preparation from the rabbit cerebral cortex. (A) 3D reconstruction of 2 pyramidal neurons superimposed on the matching minimum-intensity-projection (MIP) rendering obtained from a 250-image z-stack. The MIP algorithm searches, for each X-Y position in the stack, the darkest pixel along the z axis (the focusing plane) and assigns its value to the corresponding pixel in the final 2D image. The positions of the reconstructed neurons are indicated in the inset. (B) Two individual images from the z-stack (#27 and #58, respectively) in which dendritic spines can be appreciated (colored boxes). (C) The same 4 areas containing spines, shown at higher magnification. Scale bars: (A,B), 30 μm; (C), 5 μm.
Figure 9
Figure 9
Drawing (A) and images (B,C) of Purkinje cells and white matter (D) from a Golgi-impregnated section of the cerebellum. (A) The drawing is from an essay on the structure of the nervous system (Golgi, 1883); p refers to “protoplasmic prolongations” (dendrites) and n to the “nervous prolongation”(axon); note the arrow which denotes the flow of the nervous impulse from the dendrites to the axon (Golgi inserted similar arrows in all his other drawings of neurons in this publication). Note in (D) the meshwork of varicose fibers running in different directions. Scale bars in (B–D): 100 μm.
Figure 10
Figure 10
Images from the slides labeled as “Cajal” by Golgi (see Figure 3D), containing a section from the occipital cortex of the rabbit (A,B) and a ganglion (C), respectively. In (A,B) the asterisks mark the same field for spatial reference. See text for comments on the Cajal stain. Scale bars: 100 μm in (A,C), 25 μm in (B).
See this image and copyright information in PMC

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