neurology, and whose teaching no neurologist can sufficiently acknow

ledge, first urged the importance of classifying facts of this nature under the divisions of (A) negative, and (B) positive. Following this all-important advice, the first point is to ascertain what are the consequences of a destructive (i.e. negative) lesion of the Rolandic or

but the condition of the patient was known before the operation and the absence of conflicting facts assured.

After having thus examined the nature and value of the evidence to be brought forward, we may now enumerate the facts afforded by cases of this kind. Hughlings Jackson, the father of English

FIG. 2.--DRAWING FROM A PHOTOGRAPH (MAGNIFIED TWICE) OF THE OUTER SURFACE OF THE LEFT

HALF OF A BONNET MONKEY'S BRAIN.

R, R, R, fissure of Rolando; 8, s, s, fissure of Sylvius; IP, IP, IP, intra-parietal fissure; PO, PO, PO, parieto-occipital fissure; PC, PC, PC, præcentral sulcus.

Note.-The 'convolutions' are the portions of the cortex or surface which lie between the fissures and sulci.

so-called motor region, and especially how it affects the function of sensation. Not to weary my readers with details, many of which have a technical and not a general neurological value, the effects of such a lesion, as I have found them to exist, may be summarised as follows.

A. Effects of a Paralysing Lesion situated in a restricted part of the upper limb area in the brain—say the focus for the movements of the thumb.

(1) Insensibility to slight tactile impressions on the thumb. (2) Inability to localise correctly moderate tactile impressions on the thumb.

(3) Subjective sensation of numbness and cold 10 in the thumb. (4) Ignorance of the position of the thumb in space unless the eyes are directed towards it.

(5) Paralysis of voluntary' movement of the thumb.

The extent to which these phenomena may be developed depends upon the degree to which what we may call the thumb region of the cortex is destroyed.

In cases when the lesion affected only a small part of what may be properly termed the thumb region par excellence, I have found that the æsthesia of slight tactile impressions may fairly persist, and even enables one to more obviously appreciate the second phenomenon, i.e. the loss of the faculty of accurately localising tactile impressions on a given segment, upon which a word further must now be said. This I discovered by asking the patients, who were blindfolded, to indicate, by pointing with the forefinger of the sound hand, the actual spot previously lightly touched by the observer. The remarkable condition was then observed that the patients confidently localised the touch not on the segment actually stimulated, but one two or three segments higher." Thus, a touch on the last joint of the thumb would be in a severe case localised by the patient on the wrist. Now, these facts being observed in cases of lesions restricted to the so-called motor region show clearly that both a slight sense of touch and the power of accurately localising the same are functions of this region, and above all that their representation is, like that of movement, segmental in character. Hastening on for a moment, the third phenomenon or effect is obviously merely the intellectual appreciation of the functional

10 The representation of temperature sensory impressions was established several years ago by Herzen in the carnivora to be situated in the motor' region, but my observations in man point rather to the limbic lobe as the seat of such representa

tion.

11 Always in the hand higher than the point actually touched. The significance of this fact I shall shortly explain in another work.

defect of sensation just described; but the fourth, namely, the loss of knowledge of the position of the part, is much more important. It consists in what is most commonly called paralysis, or loss of the 'muscular sense,' inasmuch as the patient, if blind, cannot tell in what direction his thumb may be moving, or into what fresh position it may have been moved.

This defective sensory condition is still more closely associated with the paralysis of volitional movement of the part-being only well marked where the motor-paralysis is also complete-and accepting the kinesthetic view of the function of this region, it is easy to see how this intimate relationship and parallelism must exist. But we must not anticipate what follows. The last effect, namely, the paralysis of so-called ' voluntary' movement, being the most obvious and, to the patient, the most distressing consequence of the lesion, has always attracted so much attention that the conditions of tactile and muscular anaesthesia just detailed have hitherto almost escaped notice. It is doubtless owing to this that the obvious fact of motorparalysis has formed the basis of keen dispute on the subject of kinæsthesis and its relation to volition. When Bastian introduced his cogent arguments in favour of the indissoluble connection between the sensory representation of movements and the motor impulses, much discussion was excited among neurologists because the simplicity of Bell's great division of nerve function in the spinal nerve roots had led some to think that the highly complex centres in the cerebral cortex could similarly be absolutely separated into sensory centres and motor centres. Indeed, it was through this predisposition, coupled with the discovery of motor function, that the rather misleading title of motor region of the brain was applied, and is still given, to the Rolandic region of the cortex.12

The assumption of those who separate the two functions of motion and sensation and assign them to two different parts of the brain, is that the precursive sensory stage of a voluntary act is performed in the sensory perceptive centres of the limbic lobe, and that internuncial, i.e. connecting, fibres convey the efferent impulses to the by them so-called motor centres in the Rolandic region. The effects, however, of a negative or destructive lesion, already detailed above, may appear to most people to sufficiently decide the point in favour of sensory impressions being represented in the so-called motor region

12 Consideration of the manner in which nerve structure and nerve function must have been evolved, and of the constitution of the simplest nervous systems that zoology offers us, might have been thought enough to guard against the fallacies involved in what may well be called the separatist view. Nay, more, the great modern exponent of the evolution of nerve function, Hughlings Jackson, is always careful to employ the term sensori-motor in speaking of all nerve-centres, in whatever part of the nervous system may be under consideration. And, finally, it is impossible to logically conceive of a nerve-centre which has not a sensory side as well as a motor unless we are prepared to admit the doctrine of spontaneity, for the support of which not a single incontestable fact exists.