(_i_) Hallucinatory paræsthesiæ are those which are so well defined and strong as to need the aid of other senses and reasoning to convince the patient of their unreality. A peculiar example of this is what occurs after amputation of a limb: for days or weeks the lost member is felt with the utmost distinctness; the absent fingers or toes may be moved in imagination and their position described. (_j_) Delusional paræsthesiæ are such in which the patient (usually {35} insane), no longer correcting his sensations by the use of other senses and by reasoning, firmly believes in their reality—_i.e._ externality. For example: in such patients visceral sensations give rise to the belief that there is a foreign body or an animal inside the patient, or that parts are misplaced or wrenched and beaten. Pains are thought to be due to blows received or to the bites of animals or projectiles thrown upon the patient. With perversions of muscular sense an insane patient may believe that he is flying or floating in the air. In hypochondriasis many of the symptoms complained of are nothing but paræsthesiæ exaggerated by a morbid state of the mind, and sometimes created (projected) by expectant attention. The hallucinations of the insane are in great measure phenomena of this group, the projections, though special and common, never being so strong and definite as to acquire apparent objectivity. The auræ of epilepsy are paræsthesiæ. For example: a sensation in the epigastrium preceding a fit indicates an irritation at the origin of the vagus nerve and its projection as a subjective sensation at the distribution of the nerve. An auditory or visual aura similarly represents a discharge or projection from the acoustic and visual cortical areas respectively. In most cases of malingering, and in some cases of so-called railway spine, the symptoms so loudly complained of belong to the two classes of hyperæsthesiæ and paræsthesiæ; they are undemonstrable and non-measurable; only the patient himself can vouch for their reality. A diagnosis in such cases, without objective symptoms indicating well-known lesions, should be very reserved. ANÆSTHESIA, or loss of sensibility, may exist in every degree, from one so slight as to be hardly demonstrable by delicate tests to the most absolute loss of all feeling. It manifests itself in various modes corresponding to the normal physiological varieties of sensibility; in most cases the loss of feeling involves all of these, but in others they are separately affected, and we observe the following types, pure or combined: (_a_) Tactile Anæsthesia. The capacity to perceive superficial and gentle impressions upon the skin and mucous membrane, and the ability to locate and separate such impressions, may be lost, while other modes of sensibility remain normal.