abolished.* Luciani found it diminished in his three experiments on apes.t In man we have the fact that one-sided paralysis from disease of the opposite motor zone may or may not be accompanied with anesthesia of the parts. Luciani, who FIG. 20.-Luciani's Tactile Region in the Dog. believes that the motor zone is also sensory, tries to minimize the value of this evidence by pointing to the insufficiency with which patients are examined. He himself believes that in dogs the tactile sphere extends backwards and forwards of the directly excitable region, into the frontal and parietal lobes (see Fig. 20). Nothnagel considers that pathological evidence points in the same direction; ‡ and Dr. Mills, carefully reviewing the evidence, adds the gyri fornicatus and hippocampi to the cutaneo-muscular region in man.§ If one compare Luciani's diagrams together (Figs. 14, 16, 19, 20) one will see that the entire parietal region of the dog's skull is common to the four senses of sight, hearing, smell, and touch, including muscular feeling. The corresponding region in the human brain (upper parietal and supra-marginal gyri-see Fig. 17, p. 56) seems to be a somewhat similar place of conflux. Optical aphasias and motor and tactile disturbances all result from its injury, especially when that is on the left side. * Pp. 15-17. Op. cit. p. 18. The lower we go in the animal scale the + Luciani u. Seppili, op. cit. pp. 275-288. I See Exner's Unters. üb. Localization, plate xxv. less differentiated the functions of the several brain-parts seem to be.* It may be that the region in question still represents in ourselves something like this primitive condition, and that the surrounding parts, in adapting themselves more and more to specialized and narrow functions, have left it as a sort of carrefour through which they send currents and converse. That it should be connected with musculo-cutaneous feeling is, however, no reason why the motor zone proper should not be so connected too. And the cases of paralysis from the motor zone with no accompanying anesthesia may be explicable without denying all sensory function to that region. For, as my colleague Dr. James Putnam informs me, sensibility is always harder to kill than motility, even where we know for a certainty that the lesion affects tracts that are both sensory and motor. Persons whose hand is paralyzed in its movements from compression of arm-nerves during sleep, still feel with their fingers; and they may still feel in their feet when their legs are paralyzed by bruising of the spinal cord. In a similar way, the motor cortex might be sensitive as well as motor, and yet by this greater subtlety (or whatever the peculiarity may be) in the sensory currents, the sensibility might survive an amount of injury there by which the motility was destroyed. Nothnagel considers that there are grounds for supposing the muscular sense to be exclusively connected with the parietal lobe and not with the motor zone. Disease of this lobe gives pure ataxy without palsy, and of the motor zone pure palsy without loss of muscular sense." He fails, however, to convince more competent critics than the present writer,t so I conclude with them that as yet we have no decisive grounds for locating muscular and cutaneous feeling apart. Much still remains to be learned about the relations between musculo-cutaneous sensibility and the cortex, but one thing is certain: that neither the occipital, the forward frontal, nor the temporal lobes seem to have anything essential to do with it in man. * Cf. Ferrier's Functions, etc., chap. IV and chap. x, §§ 6 to 9. Op. cit. p. 17. E.g. Starr, loc. cit. p. 272; Leyden, Beiträge zur Lehre v. d. Localization im Gehirn (1888), p. 72. It is knit up with the performances of the motor zone and of the convolutions backwards and midwards of them. The reader must remember this conclusion when we come to the chapter on the Will. I must add a word about the connection of aphasia with the tactile sense. On p. 40 I spoke of those cases in which the patient can write but not read his own writing. He cannot read by his eyes; but he can read by the feeling in his fingers, if he retrace the letters in the air. It is convenient for such a patient to have a pen in hand whilst reading in this way, in order to make the usual feeling of writing more complete.* In such a case we must suppose that the path between the optical and the graphic centres remains open, whilst that between the optical and the auditory and articulatory centres is closed. Only thus can we understand how the look of the writing should fail to suggest the sound of the words to the patient's mind, whilst it still suggests the proper movements of graphic imitation. These movements in their turn must of course be felt, and the feeling of them must be associated with the centres for hearing and pronouncing the words. The injury in cases like this where very special combinations fail, whilst others go on as usual, must always be supposed to be of the nature of increased resistance to the passage of certain currents of association. If any of the elements of mental function were destroyed the incapacity would necessarily be much more formidable. A patient who can both read and write with his fingers most likely uses an identical 'graphic' centre, at once sensory and motor, for both operations. I have now given, as far as the nature of this book will allow, a complete account of the present state of the locali zation-question. In its main outlines it stands firm, though much has still to be discovered. The anterior frontal lobes, for example, so far as is yet known, have no definite functions. Goltz finds that dogs bereft of them both are incessantly in motion, and excitable by every small stimulus. They are *Bernard, op. cit. p. 84. irascible and amative in an extraordinary degree, and their sides grow bare with perpetual reflex scratching; but they show no local troubles of either motion or sensibility. In monkeys not even this lack of inhibitory ability is shown, and neither stimulation nor excision of the prefrontal lobes produces any symptoms whatever. One monkey of Horsley and Schaefer's was as tame, and did certain tricks as well, after as before the operation.* It is probable that we have about reached the limits of what can be learned about brainfunctions from vivisecting inferior animals, and that we must hereafter look more exclusively to human pathology for light. The existence of separate speech and writing centres in the left hemisphere in man; the fact that palsy from cortical injury is so much more complete and enduring in man and the monkey than in dogs; and the farther fact that it seems more difficult to get complete sensorial blindness from cortical ablations in the lower animals than in man, all show that functions get more specially localized as evolution goes on. In birds localization seems hardly to exist, and in rodents it is much less conspicuous than in carnivora. Even for man, however, Munk's way of mapping out the cortex into absolute areas within which only one movement or sensation is represented is surely false. The truth seems to be rather that, although there is a correspondence of certain regions of the brain to certain regions of the body, yet the several parts within each bodily region are represented throughout the whole of the corresponding brain-region like pepper and salt sprinkled from the same caster. This, however, does not prevent each 'part' from having its focus at one spot within the brainregion. The various brain-regions merge into each other in the same mixed way. As Mr. Horsley says: "There are border centres, and the area of representation of the face merges into that for the representation of the upper limb. If there was a focal lesion at that point, you would have the movements of these two parts starting together."† Philos. Trans., vol. 179. p. 3. Trans. of Congress of Am. Phys. and Surg. 1888, vol. 1. p. 348. Beevor and Horsley's paper on electric stimulation of the monkey's brain is the most beautiful work yet done for precision. See Phil. Trans., vol. 179, p. 205, especially the plates. The accompanying figure from Paneth shows just how the matter stands in the dog.* I am speaking now of localizations breadthwise over the brainsurface. It is conceivable that there might be also localizations depthwise through the cortex. The more superficial cells are smaller, the deepest layer of them is large; and it has been suggested that the superficial cells are sensorial, the deeper ones motor; † or that the superficial ones in the motor region are correlated with the extremities of the organs to be moved (fingers, etc.), the deeper ones with the more central segments (wrist, elbow, etc.). It need hardly be said that all such theories are as yet but guesses. We thus see that the postulate of Meynert and Jackson which we started with on p. 30 is on the whole most satisfactorily corroborated by subsequent objective research. The highest centres do probably FIG. 21.-Dog's motor centres, right contain nothing but arrangements -The points of the motor region for representing impressions and muscles: the loops with the orbi- movements, and other arrangements cularis palpebrarum; the plain crosses with the flexor, the crosses for coupling the activity of these inscribed in circles with the extensor, digitorum communis of arrangements together.§ Currents hemisphere, according to Paneth. are correlated as follows with the fore-paw; the plain circles with the abductor pollicis pouring in from the sense-organs longus; the double crosses with the extensor communis of the first excite some arrangements, hind-limb. * Pflüger's Archiv, vol. 37, p. 523 (1885). By Luys in his generally preposterous book 'The Brain'; also by Horsley. C. Mercier: The Nervous System and the Mind, p. 124. § The frontal lobes as yet remain a puzzle. Wundt tries to explain them as an organ of 'apperception' (Grundzüge d. Physiologischen Psychologie, 3d ed., vol. 1. p. 233 ff.), but I confess myself unable to apprehend clearly the Wundtian philosophy so far as this word enters into it, so must be contented with this bare reference.-Until quite recently it was |