Note 463 — Chapter XXVI · [430]

The same caution must be shown in discussing pathological cases. There are remarkable discrepancies in the effects of peripheral anæsthesia upon the voluntary power. Such cases as I quoted in the text (p. 490) are by no means the only type. In those cases the patients could move their limbs accurately when the eyes were open, and inaccurately when they were shut. In other cases, however, the anæsthetic patients cannot move their limbs at all when the eyes are shut. (For reports of two such cases see Bastian in 'Brain,' Binet in Rev. Philos., xxv. 478.) M. Binet explains these (hysterical) cases as requiring the 'dynamogenic' stimulus of light (see above, p. 377). They might, however, be cases of such congenitally defective optical imagination that the 'mental cue' was normally 'tactile;' and that when this tactile cue failed through functional inertness of the kinæsthetic centres, the only optical cue strong enough to determine the discharge had to be an actual sensation of the eye.—There is still a third class of cases in which the limbs have lost all sensibility, even for movements passively imprinted, but in which voluntary movements can be accurately executed even when the eyes are closed. MM. Binet and Féré have reported some of these interesting cases, which are found amongst the hysterical hemianæsthetics. They can, for example, write accurately at will, although their eyes are closed and they have no feeling of the writing taking place, and many of them do not know when it begins or stops. Asked to write repeatedly the letter a, and then say how many times they have written it, some are able to assign the number and some are not. Some of them admit that they are guided by visual imagination of what is being done. Cf. Archives de Physiologie, Oct. 1887, pp. 363-5. Now it would seem at first sight that feelings of outgoing innervation must exist in these cases and be kept account of. There are no other guiding impressions, either immediate or remote, of which the patient is conscious; and unless feelings of innervation be there, the writing would seem miraculous. But if such feelings are present in these cases, and suffice to direct accurately the succession of movements, why do they not suffice in those other anæsthetic cases in which movement becomes disorderly when the eyes are closed? Innervation is there, or there would be no movement; why is the feeling of the innervation gone? The truth seems to be, as M. Binet supposes (Rev. Philos., xxiii. p. 479), that these cases are not arguments for the feeling of innervation. They are pathological curiosities; and the patients are not really anæsthetic, but are victims of that curious dissociation or splitting-off of one part of their consciousness from the rest which we are just beginning to understand, thanks to Messrs. Janet, Binet, and Gurney, and in which the split-off part (in this case the kinæsthetic sensations) may nevertheless remain to produce its usual effects. Compare what was said above, p. 491.