LLAC were produced experimentally by injecting inactive bovine serum as antigen in cats. During 300 days after the last effective injection, brain water content of cats with LLCA was measured and their EEG was recorded. 1) The water content in the motor cortex of cat with LLCA tends to increase during a considerable period as 60 days after the last effective injection. This increasing is the edema type which mainly dues to that of free water. About half of this edema type shows an electroencephalographically dominant slow wave more markedly than the normal. 2) In cats with LLCA the stadium in which the title of antibody shows maximum and in which γ-globulin increases accordes with the existing time of brain edema. The antibody remains much longer. The increase of water content in the brain tissue is regarded to provocate or accerlate the convulsion. Therefore we can prove from the stand point of water metabolism in the berain tissue that the cats with LLCA is xperimentally disposed to convulsion.