The two chambers of the brain. The actual relationship between the brain and the mind has been for many centuries one of the most difficult problems of both philosophy and science, but recent research into how the two sides of the brain work in unison, or after injury separately, is beginning to throw some light on the subject.
The brain is divided into two hemispheres the left and the right and is connected to the nervous system in a crossover fashion: The left hemisphere controls the right side of the body, and the right hemisphere the left side. Because of the crossing over of the pathways, any damage or a stroke in the left hemisphere will affect the right side of the body and vice versa. In the mid-19th century, doctors learned from observation of brain injuries that visuospatial thought was mainly located in the right hemisphere and language-related capabilities mainly in the left. Because language and speech are so closely linked with thinking, reasoning, and the higher mental functions, the general view developed that the right half of the brain was the less-advanced part, with a lower level of capability than the other half. Thus the left half came to be called the major hemisphere and the right half the minor hemisphere.