Stipites laminariae was inserted in cranial cavity of dogs and its swelling by water resorption made a mechanical depression on the brain which caused motoric palsy of lower extremities. The occurence and recover of palsy was studied with the lapse of time. Also the change of nerve cells in motor cortex especially of Betz gigantic cells and the edematous change of brain tissue were timely studied. Results: 1) Intensity and duration of motoric palsy ran parallel with intensity and duration of mehanical depession of stipites laminariae. 2) The degeneration of nerve cells varied with intensity and duration of depression, but if the depression continued more than 6 hours the degree of degeneration became constant. 3) The occurence of palsy generally preceeded the degeneration of nerve cells. 4) Short duration of depression caused no severe degeneration to nerve cells. Cases in which brain edema was found intensively and widely, palsy was found. 5) Under rash and big pression the degeneration of nerve cells could be caused even by mere mechanical depsession. It was proved in autopsy. 6) It is considered that in living body the degeneration of nerve cells is caused not only by simple mechanical depression but also by lymph stagination, brain edema and the disturbances of blood supply such as acute break, anemia and congestion.