with their fellow-men is by gestures, not only use this sign, but imply
hatred also by holding the hand over the heart accompanied by the sign of
negation. Moreover, pointing to the heart accompanied by a cry of pain or
joy would indicate respectively death of an enemy or friend. Again,
primitive man protected himself from the weapons of his enemies by holding
the shield in his left hand, thus covering the heart and leaving the right
hand free to wield his spear. The question whether it would have been to
his advantage to use either hand indifferently for spear and shield has
been, to my mind, solved by the fact that in the long procession of ages
evolution has determined right-handed specialisation as being more
advantageous to the progress of mankind than ambidexterity.
Right-handedness is an inherited character in the same sense as the
potential power of speech.




LOCALISATION OF SPEECH CENTRES IN THE BRAIN


In 1863 Broca showed the importance in all right-handed people (that is in
about ninety-five per cent of all human beings) of the third _left_ frontal
convolution for speech (_vide_ figs. 16 and 17); when this is destroyed by
disease, although the patient can understand what is said and can
understand written and printed language, the power of articulate speech is
lost. _Motor Aphasia_. This portion of the brain is concerned with the
revival of the motor images, and has been termed by Dr. Bastian "the
glosso-kinæsthetic centre," or the cortical grey matter, in which the
images of the sense of movement of the lips and tongue are formed (_vide_
fig. 17). A destruction of a similar portion of the cortex in a