There is some evidence that the brain occasionally becomes overgrown in consequence of disease. This overgrowth does not consist, however, in an increase of the nerve cells and fibers of the brain, but in excessive development of the connective tissue substance of the organ. This condition is known as hypertrophy. Atrophy is the opposite condition, in which the brain becomes shrunken. The symptoms of both affections are so very obscure that they cannot be distinguished, during life, from other diseases. When atrophy affects but One side of the brain, life may be continued many years, as each half of the brain is complete in itself.