Ten per cent metrazol solution was experimental1y iniected in cat's and the changes of the ketoenolic granules (KEG) due to convulsion were histochemically investigated by the carbol fuesin jod method. 1) KEG in the nerve cells are marked1y increased in each area of the caudate nucleus by convulsion. 2) The increase is maximum at Cm., especially in its large cells. 3) KEG in the Nissl' gray sllbstance show the tendency of decreasing in eack area by convulsion, compared with non-convulsive cases, but the grade of decrease is not different among these areas. 4) From the facts above mentioned it is considered that in the caudate nucleus the Cm takcs the largest part in convulsion, especially its large cells.