CHAPTER XI HAND AND BRAIN There remains to be considered the source suggested by Professor Gratiolet, when he turned from the organs in immediate contact with the arm and hand to the cerebral centre of nerve force. The statements advanced by him that the anterior convolutions of the left side of the brain are earlier developed than those of the right, when taken in connection with the well-known decussation of the nerve-roots, would account for the earlier development of the muscles and nerves of the right arm; but his opinion has been controverted by competent observers. This, however, does not dispose of the question. The localisation of the mental operations of speaking, naming, and writing in certain specific cerebral centres, and the recognised functional relations of those word-centres with other active cerebration, have given a new significance to the vital action of the brain as the seat of nerve-force. It was only in 1861 that M. Broca definitely assigned the posterior part of the third frontal convolution of the left hemisphere as the seat of articulate speech. More recently this has been followed up by observations suggestive of some possible correlation between the reflex action of the cerebral hemispheres on the limbs; but it has thus far been no more than a passing allusion, tending to beget observation of possible coincidences, such as may be found between left-handedness and either an accompanying transposition of the seat of articulate speech to the right hemisphere, or some prevailing characteristic of the degree of word-memory in the left-handed. A recent observer, Dr. J. Batty Tuke, definitely affirms that “the large proportion of cases of ataxic aphasia occur in association with right-sided hemiplegia, although others are on record in which it has appeared in connection with left-sided hemiplegia in left-handed persons” (_Encyc. Britann._, art. “Aphasia”). In those an intimate relation is thus established between right or left-handedness and the development of the opposite cerebral hemisphere.