The man who mistook his wife for a hat by Oliver Sacks, Оливер Сакс Page B

especially that of the parietal lobes), or peripheral ones (the condition of the nerve-stump, or neuromas; nerve-damage, nerve-block or nerve-stimulation; disturbances in the spinal nerve-roots or sensory tracts in the cord). I have been particularly interested, myself, in these peripheral determinants.
       The following pieces, extremely short, almost anecdotal, come from the 'Clinical Curio' section of the British Medical Journal.
        Phantom Finger
       A sailor accidentally cut off his right index finger. For forty years afterwards he was plagued by an intrusive phantom of the finger
       rigidly extended, as it was when cut off. Whenever he moved his hand toward his face-for example, to eat or to scratch his nose- he was afraid that this phantom finger would poke his eye out. (He knew this to be impossible, but the feeling was irresistible.) He then developed severe sensory diabetic neuropathy and lost all sensation of even having any fingers. The phantom finger disappeared too.
       It is well known that a central pathological disorder, such as a sensory stroke, can 'cure' a phantom. How often does a peripheral pathological disorder have the same effect?
        Disappearing Phantom Limbs
       All amputees, and all who work with them, know that a phantom limb is essential if an artificial limb is to be used. Dr Michael Kremer writes: 'Its value to the amputee is enormous. I am quite certain that no amputee with an artificial lower limb can walk on it satisfactorily until the body-image, in other words the phantom, is incorporated into it.'
       Thus the disappearance of a phantom may be disastrous, and its recovery, its re-animation, a matter of urgency. This may be effected in all sorts of ways: Weir Mitchell describes how, with faradisation of the brachial plexus, a phantom hand, missing for twenty-five years, was suddenly 'resurrected'. One such patient, under my care, describes how he must 'wake up' his phantom in the mornings: first he flexes the thigh-stump towards him, and then he slaps it sharply-'like a baby's bottom'-several times. On the fifth or sixth slap the phantom suddenly shoots forth, rekindled, fulgurated, by the peripheral stimulus. Only then can he put on his prosthesis and walk. What other odd methods (one wonders) are used by amputees?
        Positional Phantoms
       A patient, Charles D., was referred to us for stumbling, falls and vertigo-there had been unfounded suspicions of labyrinthine disorder. It was evident on closer questioning that what he experi-
       enced was not vertigo at all, but a flutter of ever-changing positional illusions-suddenly the floor seemed further, then suddenly nearer, it pitched, it jerked, it tilted-in his own words 'like a ship in heavy seas'. In consequence he found himself lurching and pitching, unless he looked down at his feet. Vision was necessary to show him the true position of his feet and the floor-feel had become grossly unstable and misleading-but sometimes even vision was overwhelmed by feel, so that the floor and his feet looked frightening and shifting.
       We soon ascertained that he was suffering from the acute onset of tabes -and (in consequence of dorsal root involvement) from a sort of sensory delirium of rapidly fluctuating 'proprioceptive illusions'. Everyone is familiar with the classical end-stage of tabes, in which there may be virtual proprioceptive 'blindness' for the legs. Have readers encountered this intermediate stage-of positional phantoms or illusions-due to an acute (and reversible) tabetic delirium?
       The experience this patient recounts reminds me of a singular experience of my own, occurring with the recovery from a proprioceptive scotoma. This was described (in A Leg to Stand On) as follows:
       I was infinitely unsteady, and had to gaze down. There and then I perceived the source of the commotion. The source was my leg-or, rather, that thing, that featureless cylinder of chalk which served as my