(_c_) Olfactory Apparatus.—Hyperæsthesia of this sense is at present considered more a personal peculiarity than as a symptom of disease. Paræsthesiæ show themselves as subjective odors of various sorts, and when transient may be an olfactory aura preceding epileptic attacks. In conditions of organic disease subjective odors may coincide with complete loss of smell. Anæsthesia of the olfactory nervous apparatus may be due to (1) strictly local disease in the nose, catarrh, etc.; (2) to anæsthesia of the trigeminus nerve and consequent local lesions; (3) to a truly nervous lesion affecting the olfactory nerves, the olfactory bulbs, the olfactory tracts, or, lastly, the cortical centre for smell (at present unknown in man). The two last morbid conditions are usually unilateral, and coexist with subjective odors. (_d_) Gustatory Apparatus.—In this sense hyperæsthesia is clinically unknown, though as a result of education extreme delicacy of taste, a relative hyperæsthesia, may be produced. Paræsthesiæ are rare. In two cases in which we have observed the symptom (one of neurasthenia, the other of hypochondriacal melancholia) it consisted in a constant and most distressing sweet taste. The application of the galvanic current at the base of the brain, under the jaw, on the cheeks, and within the mouth produces subjective tastes of an acid or metallic nature. Anæsthesia of the gustatory nerve occurs after section of the lingual branch of the trigeminus—an operation sometimes done for lingual neuralgia, in which case the frontal two-thirds of the tongue on one side loses its property of perceiving taste. As the result of central disease next to nothing is known of this symptom. It is probable that sweet and acid tastes are perceived in the mouth and forward part of the tongue; bitter tastes on its caudal (posterior) third and in the throat (glosso-pharyngeal nerve). In the insane, paræsthesiæ and anæsthesia give rise to a great variety of delusions about the state of the parts, the nature of their food, poison in the food, etc. As a part of typical complete hemianæsthesia the special senses are {42} involved. When of hysterical origin the whole retina of one eye is generally devoid of sensibility, or it does not perceive colors. When the hemianæsthesia is due to a lesion of the caudal part of the internal capsule (organic anæsthesia), we should expect to find lateral hemianopsia, with dark half-fields on the same side as the cutaneous anæsthesia. We would not be understood as claiming that this point of distinction is as yet positively determined, but would advance it suggestively, subject to the result of observations on new cases. III. Motory Symptoms.