(_b_) Hyperalgesia, often coinciding with (_a_), is that condition in which pain is produced by excitations so slight that they would not affect a healthy nervous apparatus: it is commonly designated as tenderness. Acute and dull, superficial and deep tenderness should be sought for and distinguished, as having different values in diagnosis. A type of deep tenderness is that found upon pressing steadily upon a diseased nerve-trunk. Acute superficial hyperalgesia is best studied in cases of trigeminal neuralgia and spinal irritation. Occasionally, universal hyperalgesia is met with, usually in hysterical women. (_c_) Hyperæsthesia to thermal impressions is ordinarily shown with reference to cold. In cases of neuralgia or neuritis cold is felt excessively and painfully; in some cases of posterior spinal sclerosis there is the greatest dread of draughts of cold air, and patients protect their legs in an extraordinary manner. (_d_) Hyperæsthesia of the muscular sense.[3] The special sensations or notions of muscular states and activities which we possess may be considerably exalted, as shown by greater delicacy and rapidity of movements, and by the abnormally acute way in which perceptions of form and dimensions are obtained by the subject without assistance from other senses. Examples of this condition are met with in hysteria and hypnotism. [Footnote 3: This term is employed as clinically sufficient. It is impossible in this article to enter into a consideration of the various theories held with reference to the function in question, whether it be psycho-motor, psycho-sensory, or a true muscular sensibility. It certainly differs much from the various forms of common sensibility, and has special paths.] (_e_) Visceral hyperæsthesia is chiefly shown by abnormal consciousness of the presence and action of an organ. Visceral pain usually accompanies this, and is the more prominent symptom. (_f_) Increased reflex actions (emotional, motor, vaso-motor, and {33} secretory) rarely fail to accompany hyperæsthesia in its various forms. In the hypnotic exaltation of muscular sense remarkable psychic effects may be induced, partly in a reflex way, but perhaps chiefly through the law of association. PARÆSTHESIÆ are sensations which arise centrally in nerve-fibres or nervous centres, and are projected outward and referred to the periphery or surface by consciousness, in obedience to the general law of outward projection of sensations in the Ego. They may be produced by external agencies or arise centrally without demonstrable cause. Their number and variety are very great, varying somewhat with the descriptive powers and self-consciousness of the patient, the chief being pain, formication, numbness, coldness and heat, constriction and distension, malposition, imaginary movements, etc. etc.