Doses which disturb the digestive and circulatory systems - 10 to 20 min - may cause not only giddiness, but also a sense of constriction and heaviness of the head, prominence of the eyes, some confusion of intellect, and muscular weakness. Upon which part of the nervous system the special effects of larger doses are exerted - whether upon the vagus, the nerve-centres, or the peripheral nerves - has been disputed.