Dendrite anastosome in rabbit pancreas

Cajal wrote,

"The structural figures accompanying the text, which appear highly schematic, are in fact less so than the actual preparations."

What is remarkable is that someone else looking at the same preparation would see an impossible tangle of fibers, where Cajal saw a highly schematic layout. Was his world more highly schematic than his figures? Cajal had the gift of transforming his ideas into drawings. His captions and choice of upper or lower case lettering point out the salient features to the reader.

At the end of the nineteenth century, a central question was whether axons form a continuous reticulum (plexus), or do axons end freely? Golgi believed that the nervous system was a plexus of interconnected cells, whereas Cajal believe that it was a collection of individual cells. Using Golgi's technique, Cajal demonstrated the absence of continuity between cells, an idea which has led nearly all the succeeding neuroscientists to think about the brain as a collection of individual neurons instead of a reticulm. In other words we conceptualize the nervous system like a republic. Cajal spent most of his life arguing in favor of this theory, but the figure below shows that Cajal seems to have taken the reticular theory very seriously. Perhaps Cajal drew Figure 40 on a day when he was thinking that Golgi might be correct. In Fig 40, Cajal concedes that a true plexus of nervous fibers may be found in the rabbit pancreas. He refers to the dendrite-dendrite connection as an "anastomose" happening in the pancreas.

Another aspect of Golgi's reticular theory was that the dendrites serve a nutritive function. Golgi had observed a tendency for dendrites to cluster around blood vessels and neuroglial cells. As if in tribute to his contender's ideas, Cajal illustrates a dendrite that is located in the wall of an artery (figure above, neuron E), where it has a close relationship with the nutrients in the blood stream. Even though Cajal generally thought of the dendrites as receiving centers for synaptic transmission, Fig 40E seems to express his acknowledgement of dendrite-vasal relationships.

Many scientists think that the acknowledgement of neuronal theory by Cajal versus the reticular theory by Golgi implies the absolute impossibility of synctium formation in the nervous system. However there is much data showing the formation of bonds between neurons that consist of smooth processes without classical synapses.

Reference

Ramon y Cajal, Santiago. N., Swanson, L. W., (Eds.) 1990. New ideas on the structure of the nervous system in man and vertebrates. MIT Press, Cambridge.