大腦皮質の構成と機能に就いて

On the Organization and Functions of the Cerebral Cortex

　身体の他の部分とは比較にならない程の，大脳皮質のおどろくべき膨脹は，それが人類の働きにとつて基本的な重大性を持つことを物語るものであつて，その構造は夙に生物学者達の興味を惹いたものである．と云うのは，如何なる器官においても，それが活溺するエネルギーを介して，構造が機能の様式を決定するからである．而して紳経組織は通報と連絡の單官なるが故に，大脳皮質については，明らかに2つの研究さるべき側面があつた．1つはその固有な内部構造・他は外部との連絡である．

　大脳皮質の構造に関する初期の研究は，肉眼乃至虫メガネをもって試みられた．そしてこの方法によつて既にBaillarger（1840）は，大脳皮質の大部分に6つの水平層を弁別し更に．その前に，Gennariは後頭部にある特異な変形を見出している．それは今日のStriate　areaに該当する．この種の研究はElliot　Smith（1907）に至つて頂点に達し，自ら検証したBaillargerの基本的構造の種々相に基いて，大脳皮質の膨大な地図が作製された．

The cerebral cortex develops by evagina-tion and elaboration of the lateral walls of the endbrain. The earliest evaginations become the olfactory bulbs. At the base of the olfactory bulbs lies a complex second olfactory area which is invaded and expan-ed by various nonolfactory systems and this correlation tissue is evaginated and elaborated to form the cerebral hemisphe-res. The gray matter covering the latter is called the cortex or pallium. The older olfactory portion-archipallium, allocortex-is later pushed to the periphery and comple-tely overshadowed by the vast expansion of the neopallium, called the isocortex be-cause at some time in its ontogenetic deve-lopment it has a typical six-layered structu-re. This thin sheet of correlation tissue seems well adapted to the labile type of behavior which we call intelligent and ca-pable of indefinite expansion (Herrick,-'21).

The tremendous increase in size of the cerebral cortex in relation to the rest of the organismis evidence of its fundament-al importance to the functioning of the human organism and biologists early beganto be curious about its structure since the structure of any organ imposes on the energy it utilizes the order of its func-tioning. Because the nervous tissue is an organ of communication and interrelation it was obvious that there were two aspects of the cortex which had to be investigated —its intrinsic structure and its external con-nection.