The mental changes which accompany disturbances of the viscera may be classified under two groups, as follows:— (a) Those changes which accompany the disease directly, and are associated with the presence of some abnormal product or tissue change produced directly by the disease (for example, myxædema). These may be called the direct mental effects of visceral disease, and will be neglected in this communication. (b) Certain mental changes which are only present in those cases where the visceral disturbance causes what is known as referred pain associated with tenderness of the superficial structure of the body and scalp. Now this pain and tenderness are due to changes in some part of the central sympathetic system caused by disturbance of the internal organ to which sensory sympathetic nerves are supplied. Thus the mental changes of this group may be said to be indirect, for they are associated with visceral disturbances through the mediation of the sympathetic system. In this communication only the sensory and emotional changes are considered.