Ancient Greece

After hundreds of years believing that the brain had no value, the Greeks first began investigating the brain as the center of consciousness and physical functioning around 700 B.C.E.

Alcmaeon and the Importance of the Brain

Alcmaeon of Croton

In the 6th century B.C.E., Alcmaeon of Croton was the first Greek philosopher-scientist to publish a book that firmly established the brain as the “seat of understanding” (Huffman, 2008). It is believed that he was the first to discover that all sensory organs, such as the eyes, were connected to the brain via channels, or poroi, which, in the example of eyes, equates to the optic nerve (Neurosurgery Editorial Office, 2010). He is also attributed with the naming of four out the five senses (sight, hearing, taste, and smell) in understanding sensation and perception. Later philosophers, such as Plato, would come to use the concept of the brain as one of the most important organs, responsible for understanding and intelligence. Interestingly enough, Aristotle, as a contemporary of Plato, never embraced the belief in the brain as the center of sensation, but maintained that the heart was the center.

 Hippocrates and the Origin of Epilepsy

File:Hippocrates rubens.jpgHippocrates of Kos

Hippocrates, another believer in the importance of the brain in physical and psychological functioning, began challenging the origins of what was then known as the Sacred Disease (epilepsy). Until he wrote “On the Sacred Disease” in 400 B.C.E., it was widely believed that epilepsy was caused by vengeful gods. Hippocrates dismissed those who believed in divine origin of disease as charlatans.  Among the evidence for epilepsy originating in the brain, he also gave a highly detailed description of the anatomy of the brain and vascular system. In “On the Sacred Disease” (Translated by Francis Adams) he wrote:

But the brain is the cause of this affection, as it is of other very great diseases, and in what manner and from what cause it is formed, I will now plainly declare. The brain of man, as in all other animals, is double, and a thin membrane divides it through the middle, and therefore the pain is not always in the same part of the head; for sometimes it is situated on either side, and sometimes the whole is affected; and veins run toward it from all parts of the body, many of which are small, but two are thick, the one from the liver, and the other from the spleen. And it is thus with regard to the one from the liver: a portion of it runs downward through the parts on the side, near the kidneys and the psoas muscles, to the inner part of the thigh, and extends to the foot. It is called vena cava. The other runs upward by the right veins and the lungs, and divides into branches for the heart and the right arm. The remaining part of it rises upward across the clavicle to the right side of the neck, and is superficial so as to be seen; near the ear it is concealed, and there it divides; its thickest, largest, and most hollow part ends in the brain; another small vein goes to the right ear, another to the right eye, and another to the nostril. Such are the distributions of the hepatic vein. And a vein from the spleen is distributed on the left side, upward and downward, like that from the liver, but more slender and feeble.

This description is a vast improvement on the writings of the Edwin Smith Surgical Papyrus, and a greater expansion on Alcmaeon’s discovery of the connections between sensory neurons to the brain. However, due to the refusal to dissect anything, the section after this attributes epilepsy to an excess of phlegm, and provides a description of the four humors (blood, phlegm, black bile, yellow bile).

Galen and Cranial Nerves

File:Galen detail.jpgClaudius Galen

Despite his subscription to bodily humors, Claudius Galen has the longest lasting effect on the history of neuroscience (Gross, 1987). He is attributed with the discovery and distinction between motor and sensory neurons. Galen did believe in dissection as a valid means of obtaining greater understanding of anatomy; however, he dissected mostly apes and pigs, and extended his findings to human beings. His discoveries and beliefs prevailed over all other beliefs in neurology, and were not widely questioned until the 16th century.

 

Resources

Gross, C. G. (1987). Early History of Neuroscience. In Adelman, G. (ed.), Encyclopedia of Neuroscience, 843-847.

Huffman, C., (2008).  Alcmaeon. The Stanford Encyclopedia of Philosophy, Zalta, E. N. (ed.). Retrieved from http://plato.stanford.edu/archives/win2008/entries/alcmaeon/

Neurosurgery Editorial Office, (2010). Alchmaeon of Croton. Retrieved from http://neurosurgerycns.wordpress.com/2010/02/08/free-article-alcmaeon-of-croton/

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