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In this paper it will be necessary to enter on minute details of the anatomy; but they regard a subject hitherto untouched, although essential to the comprehension of the nervous system, without which, indeed, it could not be said that we had a know­ ledge of the nerves as a system. The author has advanced, by slow and laborious researches, from observing the general arrangement of the nerves as they lie in the body, to the investigation of par­ticular nerves and their endowments; and, finally, to the examination of these parts in the centre of the system, the brain and spinal marrow, which enables him to assign the reason of that perfect symmetry which reigns through the whole.

The concept of consolidation, or fixation, of memory is historically linked to the effects of disruptive agents on the brain and their interpretation. For example, retrograde amnesia seen in man following physical trauma has been interpreted to indicate that permanent memory normally forms following a learning experience. This idea was subsequently expanded by evidence for a temporal gradient of growing insusceptibility to disruption of newly-formed memory in both man and in experimental animals. Agents producing convulsions and unconsciousness, such as electroconvulsive shock, were reported to produce varying degrees of performance decrement as a function of the time of their administration. The question remained whether some unitary or multiple process of memory fixation existed or alternatively, whether the various disruptive agents had noxious properties that interfered with registration, storage or retrieval of behavioral information.

The reflex activity of the nervous system is one of its most remarkable properties, and as such has engaged the earnest attention of scientists. On the clinical side the discovery of reflex pupillary changes in disease, particularly the phenomenon of Argyll-Robertson and the elicitation of the knee-jerk by Erb and Westphal, opened up a field of research work the results of which make up a large part of our present day neurological diagnostic means. The discovery of the ankle-jerk by Gowers and the establishment of its great clinical value by Sarbo, Ziehen and others; the remarkable great-toe phenomenon of Babinski and its modified forms as elicited by the technic of Oppenheim and Gordon, stimulated a great many workers and at the present time almost all the cutaneous surfaces and tendons have been searched for characteristic reflex phenomena. A group of reflexes which has with all this research activity received only

While increases in spontaneous activity have been demonstrated following scopolamine administration in mice (Morpurgo & Theobald, 1964) and rats (Tapp, 1965; Payne & Anderson, 1967a; Meyers et al, 1964) such a demonstration has never been made in the gerbil.

Since the communication above referred to was presented to the Royal Society, I have made a very minute dissection in alcohol of the whole nervous system of the young heifer’s heart. The distribution of the ganglia and nerves over the entire surface of the heart, and the relations of these structures to the blood-vessels and muscular substance, are far more fully displayed in these preparations than in any of my former dissections. On the anterior surface, there are distinctly visible to the naked eye ninety ganglia or ganglionic enlargements on the nerves, which pass obliquely across the arteries and the muscular fibres of the ventricles from their base to the apex. These ganglionic enlargements are observed on the nerves, not only where they are crossing the arteries, but where they are ramifying on the muscular substance without the blood-vessels. On the posterior surface, the principal branches of the coronary arteries plunge into the muscular substance of the heart near the base, and many nerves with ganglia accompany them throughout the walls to the lining membrane and columnse carneæ. From the sudden disappearance of the chief branches of the coronary arteries on the posterior surface, the nervous structure distributed over a consider­ able portion of the left ventricle is completely isolated from the blood-vessels, and on these, numerous ganglionic enlargements are likewise observed, but smaller in size than the chains of ganglia formed over the blood-vessels on the anterior surface of the heart. In the accompanying beautiful drawings, Mr. West has depicted with the greatest accuracy and minuteness the whole nervous structures demon­strable in these preparations on the surface of the heart. But the ganglia and nerves represented in these drawings constitute only a small portion of the nervous system of the heart, numerous ganglia being formed in the walls of the heart which no artist can represent. It can be clearly demonstrated that every artery distributed throughout the walls of the Uterus and Heart, and every muscular fasciculus of these organs, is supplied with nerves upon which ganglia are formed.

The influence of the nervous system over the metabolism of the carbohydrates was demonstrated by Claude Bernard’s famous piqûre experiment (1855) many years before that of hormones, but recently attention has been paid mainly to the latter. As our knowledge of the influence hormones in general has expanded, the possibility that the activities of the glands which produce them are regulated through the nervous system has been considered, and the question arises whether it is indirectly through this control that the nervous system affects carbohydrate metabolism. It was with the object of solving this question that the present research was primarily undertaken. Our original plan was to investigate the nature of the changes in carbohydrate metabolism brought about by piqûre, but we very soon found that this operation, as usually practised, is uncertain in its results and, moreover, that it is impossible to differentiate these results from the disturbances in carbohydrate metabolism which anæsthesia in itself induces. This led us to adopt the method of decerebration rather than piqûre and, by its use, we have succeeded both in localising within fairly narrow limits, the part of the brain which is principally concerned with the nervous control of carbohydrate metabolism and in throwing some light on the nature of the biochemical changes over which this control is exercised. In the present paper, we will first of all give a brief account of the experiments which led us to adopt the decerebration method rather than that of piqûre, and then consider more in detail the results which have enabled us to localise the diabetic centre. In subsequent papers we will deal with the metabolic disturbances resulting from the decerebration and with the modification of these disturbances which occur when the nervous pathways through which the centre exercises its control are interfered with.

Mr. Knight, in the papers formerly communicated by him to the Royal Society, endeavoured to prove that the fluid by which the va­rious parts added to trees, &c. are generated, has previously circu­lated through their leaves, either in the same or in the preceding season, and has subsequently descended through their barks. There is, however, a circumstance stated by Hales and by Du Hamel, which appears to militate against the above hypothesis, namely, that when two circular incisions are made, at a small distance from each other, through the hark, round the stem of a tree, and the bark between these incisions is wholly taken away; that portion of the stem which is below the incisions continues to live, and to increase in size, though much more slowly than the parts above the incisions. The above-mentioned naturalists have also observed, that a small elevated ridge is formed round the lower lip of the wound, which makes some slight advances to meet the hark and wood, projected in larger quantities from the upper lip of the wound. Our author, in a former paper, attempted to explain the above cir­cumstance, by supposing that a small part of the true sap, descending from the leaves, escapes downwards, through the porous substance of the alburnum: in another paper he has shown, from the growth of inverted cuttings, the existence of a power in the alburnum to carry the sap in different directions; and he now describes some ex­periments made in order to show that the conclusions drawn by him are not inconsistent with the facts stated by Hales and Du Hamel; and that although the ascending sap usually rises through the al­burnum and central vessels, yet the alburnous vessels appear to be also capable of an inverted action, when such action becomes neces­sary to preserve the existence of the plant.

The general characteristics of the muscular manifestations, which ensue on faradic stimulation of cerebellar nuclei, were described in a previous paper (28). In the present investigation an analysis of the nuclear responses was affected by recording the changes in tone in individual muscles of the foreand hindlimbs. Prior to our own work faradic stimulation had been applied to the cerebellar nuclei by Horsley and Clarke (17); they did not record the muscular changes graphically, but only observed the movements of the limb; these movements, to judge from their somewhat casual report, resembled those observed by ourselves. The belief that the responses observed by Horsley and Clarke were evoked by actual stimulation of the nuclei was clearly implied in their article; but in a paper by R. H. Clarke (6), published posthumously, the opinion is expressed that the reactions, supposedly of nuclear origin, were of a fallacious character, depending on current diffusion to Deiter's nucleus and various motor centres. Speaking more particulary for our own work we must state positively that our reactions were evoked by stimulation of the intracerebellar nuclei themselves, and were not due in any sense to spread of current beyond the cerebellum. Phenomena caused by spread of current are readily recognisable, and were avoided by using currents of threshold value for the nuclei, the excitability of which was carefully preserved. Our conclusions are thus more nearly in agreement with those of Horsley and Clarke than with those recorded in the posthumous paper of Clarke.

The experiments described in the preceding four papers bear on various problems presented by reflex activity. Their results confirm some of the inferences already drawn elsewhere from other experimental work, and they allow certain further inferences. A brief prefatory statement of all these inferences and of the experimental evidence which allows them will advantageously introduce the description of the processes set up in the ipselateral flexor centres of the spinal cord by a single centripetal volley and by a single antidromic volley. Then, finally, discussion of the theories of reflex excitation can be undertaken in the light of the present experimental observations. the statement treats of the subject in its present phase only; the references to relevant papers are therefore restricted in the main to the more recent ones. II. Inferences from Experimental Observations. 1.The convergence of Different Afferent Paths on the same MotoneuronesThe following evidence shows that this occurs:- (a)Histological.-Each motoneurone receives its “boutons terminaux” from many individual afferent terminals (Cajal, 1903). (b)Physiological.-Centripetal volleys set up indifferentafferent nerves excite the same motoneurones (Camis, 1909; Cooper, Denny-Brown, and Sherrington, 1926; 1927; Sherrington, 1929; Cooper and Denny-Brown, 1929 ; Eccles and Sherrington, 1930 ; 1931,a; 1931,b).

The object of the present paper is to define by histological methods the exact limitations of the visuo-sensory area of the human cortex cerebri. The investigation to be described has occupied upwards of three years. It was commenced during the summer of 1896 in the pathological laboratory of the County Asylum, Rainhill, Lancashire; it was continued during the next three years in the physiological laboratory of Mason University College, Birmingham; and it has been completed in the pathological laboratory of the London County Council at Claybury. Owing to the remarkable facilities for research granted to workers in the last-named laboratory, it has been possible to bring this investigation to a much more rapid conclusion than would otherwise have been possible. A general summary of the paper follows this introduction, and it is succeeded for convenience of reference by a list of the sections into which the paper is divided.

The present paper deals with some features of inhibitory relaxation of muscular contraction as observable in the knee extensor (decerebrate cat) when the crossed extensor reflex is subjected to inhibition by stimulation of an afferent nerve of the ipsilateral limb. The myograms have been obtained with the isometric optical myograph described in a previous paper, and the method of preparation, etc., has been as before. I.Relaxation-speed under Strong Inhibition. The speed of the muscular relaxation produced by the inhibition is often notably high. It then compares in rate with that of the lapse of a peripheral tetanus at cessation of the faradic stimulation of the muscle’s motor nerve (19).

The intention of the author in the present paper, is, not to bring forwards any new facts, but to take a general review of the inferences deducible from the series of facts detailed by him in previous papers communicated to this Society. He divides the nerves into two classes, essentially differing in their functions. The first comprehends those nerves, which, proceeding directly from the brain and spinal cord to other parts, convey in the one case to those parts the influence of those organs only from which they originate, and thus excite to con­traction the muscles of voluntary motion ; and in the other case transmit to the sensorium impressions made on the parts to which they are distributed. The second class comprises what may betermed the Ganglionic nerves, or those which enter ganglions, pro­perly so called; that term being limited to such protuberances only as receive branches of nerves proceeding from the brain and spiral cord. These nerves are distributed more especially to the vital or­ gans, as the thoracic and abdominal viscera, and to the muscles sub­servient to their functions. The nerves belonging to this class also convey impressions to the sensorium, and occasionally excite the muscles of involuntary motion, which, in common with all muscles, possess an inherent power of contractility dependent solely on their own mechanism, and which in ordinary cases are excited by stimuli peculiar to themselves. But the most important function of the gan­glionic nerves, is that of supporting the processes of secretion and assimilation, which require for their performance the combined influ­ence of the whole brain and spinal cord. Viewed as a whole, the system of ganglionic nerves, therefore, constitutes, in the strictest sense, a vital organ. Thus the sensorium, though connected by means of the cerebral and spinal nerves only partially with the organs of sense and voluntary motion, is, by means of the ganglionic nerves, connected generally with all the functions of the animal body. Hence affections of the stomach and other vital organs extend their influence over every part of the frame; while those of a muscle of voluntary motion, or even of an organ of sense, although possessing greater sensibility, are confined to the injured part. From a due consideration of the phenomena of the nervous system, it would appear that they imply the operation of more than one prin­ciple of action. The sensorial power is wholly distinct from the ner­vous power; the former residing chiefly in the brain, while the latter belongs equally to the spinal cord and brain, and may be exercised independently of the sensorial power. In like manner, the muscular power resides in the muscles, and may be called into action by various irritations independently of the nervous power, though fre­quently excited by the action of that power. The muscles of volun­tary motion are subjected to the sensorial power through the inter­vention of the nervous system; and those of involuntary motion are also, under certain circumstances, capable of being excited through the nerves by the sensorial power, particularly when under the influ­ence of the passions. The same observation applies also to other actions which properly belong to the nervous power, such as the evolution of caloric from the blood, and the various processes of se­cretion and of assimilation. That the nervous power is in these instances merely the agent of other powers, and is independent of the peculiar organization of the nerves, is proved by the same effects being produced by galvanism, transmitted through conductors diffe­rent from the nerves. The successive subordination of these several powers is shown during death, when the sensorial functions are the first to cease, and the animal no longer feels or wills, but yet the nervous power still continues to exist, as is proved by the nerves be­ing capable, when stimulated, of exciting contractions in the muscles, both of voluntary and of involuntary motion,of producing the evolution of caloric and of renewing the processes of secretion. In like manner the power of contraction, inherent in the muscular fibre, survives the destniction of both the sensorial and nervous powers, having an existence independent of either, although in the entire state of the functions they are subjected to the entire influence of both.

SUMMARYTwo factors have stimulated the present intense investigation of acrylamide neurotoxicity. These are the health hazard accompanying the vast and increasing industrial production of acrylamide, and the promise of illuminating the mechanism of dying-back disease in the human nervous system by employing acrylamide as an experimental tool. The present paper discusses the industrial uses of acrylamide, its regulation, and the prevention, detection and clinico-pathologic features of human intoxication. Bearing on the cumulative nature of acrylamide neurotoxicity, separate sections review the chemistry, biochemistry, toxicology and metabolic fate of acrylamide. Clinical, electrophysiological and morphologic data on acute and chronic acrylamide intoxication of experimental animals, and possible etiologies of nervous system damage, are considered in detail in a companion paper (P. S. Spencer and H. H. Schaumburg, Canadian Journal of Neurological Sciences, 1:151, 1974).

Three pigeons with a history of attacking a mirror target, and two of six pigeons with no prior exposure to targets, attacked a colored photograph of a conspecific during exposure to intermittent schedules of reinforcement for key pecking. Rate of attack on the photograph decreased when the reinforcement schedule was removed. The topography, temporal pattern, and locus of attack on the picture were comparable to schedule-induced attack on live, stuffed, and mirror targets. When silhouette, outline, and plain paper targets were used, schedule-induced attack was more sensitive to a change in target characteristics with a concurrent target-preference procedure than with an analogous successive-testing procedure. The combined results of the two testing procedures indicated that an “upright” white-on-black silhouette of a pigeon with or without an eye was more effective in controlling attack than was a comparable “inverted” silhouette, an outline of a pigeon, or a piece of colored paper.

The observations with which the present communication deals were met with in experiments continuing those on reciprocal innervation of symmetrical muscles. In my previous paper on that subject it had been reported that in regard to symmetrical extensors of the knee the ratio borne by intensity of the ipsilateral inhibition to the contralateral excitation is such that with equal stimuli to right and left symmetrical afferent nerves there is inhibitory suppression of contraction in both the muscles. In other words, under double reciprocal innervation the ipsilateral inhibition by each nerve completely overcomes the contralateral excitation of the other. It was shown that this mutual suppression holds over a wide range of the scale of intensities of stimulation. It was also shown that with quite weak stimuli a simultaneous stimulation of both nerves, stimuli being equal in intensity, often results in concurrent contraction of both muscles. Indeed, with quite weak stimuli, the effect of stimulation of each afferent nerve by itself is, in the decerebrate preparation, usually contraction of the ipsilateral as well as of the contralateral muscle. This being so, it is evident that at some point in the scale of intensities of stimulation there should be a place below which contralateral excitation is stronger than ipsilateral inhibition, whereas above it ipsilateral inhibition is stronger than contralateral excitation.

During the past few years, one of us (F. W. M.) has had exceptional opportunities of seeing patients suffering from various mental complaints, and of comparing the results of post-mortem examinations with the symptoms exhibited during life. One of the commonest complaints seen in the London County Asylums is General Paralysis of the Insane, and it was with a view of elucidating some of the pathological problems connected with this disease that the present enquiry was originally undertaken. How far this object has been attained will be discussed at the conclusion of the paper. The disease is one which is characterised by an extensive degenerative and wasting process occurring in the cerebral cortex, especially in the frontal and central convolutions ; during the course of the disease there are frequent seizures of a congestive, epileptiform or apoplectiform kind, and after the recovery of the patient from each of these fits, he is, as a rule, worse mentally. Each fit probably indicates the breakdown of a new focus of cerebral matter. The disease is a premature, primary, progressive decay of the neuron affecting especially those structures which have been developed latest. It is a para-syphilitic affection like tabes, with which it is, pathologically speaking, identical.

The constitution of the enteric plexuses (the plexus myentericus or plexus of Auerbach and the plexus submucosus or plexus of Meissner) and their rôle in the initiation and regulation of the gut-movements are problems which have been discussed by numerous investigators, and the literature relating to them is voluminous. Nevertheless, it can hardly be said that there is even to-day any general consensus of opinion in regard to them. The work detailed in the present paper arose out of an endeavour to provide demonstration reparations of the gut-plexuses for teaching purposes. Eventually, with the generous and unstinted help of the late Prof. N. Kulchitsky, a method of partially isolating the plexuses and of staining them with a modified Bielchowsky silver technique was evolved, which yielded preparations of such excellence that I was induced to make the attempt to work out their histological constitution. I propose to give first of all a very brief summary of the purely histological results obtained by previous workers in this field, and later, when setting forth my own observations, to deal more in detail with the related literature.

The following research was carried out in consequence of suggestions made to me by Professor Victor Horsley, to whom I wish to express my thanks for placing the facilities of his laboratory at my disposal, and for his advice and criticisms during the prosecution of the work and in the preparation of the paper. I also wish to return my best thanks to Professor Johannes Gad, in whose laboratory tire first part of the work was carried out, for his ever-ready and constant help and advice. I have further to thank my friend Dr. Risien Russell for his kindness in assisting me in some of my earlier experiments on the monkey. The researches were undertaken with the view of throwing light upon the degree to which certain movements or, speaking more precisely, sensori-motor (kinæsthetic) phenomena are represented in any given segment of the lumbo-sacral region of the mammalian spinal cord, and further what relationship exists between the representation of one movement and that of another. It is clear that at least three methods suggest themselves as means whereby this problem may be attacked, e. g. , (1) the excitation method, (2) the method of exclusion by ablation, and (3) the so-called degeneration method. Of these Nos. (2) and (3) have been already in part employed (No. (2) Sherrington, Risien Russell, No. (3) Grünbaum), but believing that with suitable precautions more exact localisation could be obtained by the excitation method, I have so far adopted that alone.

SENSORY NERVE ACTION POTENTIALS IN PATIENTS WITH PERIPHERAL LESIONS1 Authors : Gilliatt RW, Sears TA Published : 1958 Dr Thomas Sears recalls his 1958 paper and discusses the clinical, physiological and technical background from the perspective of a basic scientist Graduating in 1952, I could hardly have known that 60 years on I would be writing about this 1958 paper!1 Had he lived, Roger Gilliatt would have provided a secure clinical perspective. Of necessity, my commentary reflects on the clinical, physiological and technical background from the perspective of a basic scientist. Initially my post at ‘Queen Square’ was physiologist in the EEG department under Dr ‘Bill’ Cobb, a distinguished electroencephalographer and electromyographer. In Stockholm, Bill had collaborated with Eric Kugelberg studying the post-ischaemic repetitive firing of motor nerve fibres after a pressure cuff is released.2 Their use of two cuffs with pressure first released in the proximal one proved, (a) that the repetitive discharges arose in axons at the local site of compression induced ischaemia; (b) that conduction velocity slows through that region; and (c) that such repetitive activity of sensory fibres would explain and support Merrington …

Many books have been written on colour vision; not so many on the appreciation of form and shape. Few have dealt exclusively with the perception of fine detail. All the experiments described in this paper have one object in view, namely, to elucidate some of the mechanisms, both nervous and otherwise, by which the image formed on the retina is clarified and improved before it reaches the higher centres of the brain. Brief reference must now be made to some of the difficulties encountered during the performance of the experiments described in this paper. These were of three kinds: apparatus, research rooms, assistants, When in 1939 the pre-medical branch of St Bartholomew’s Hospital Medical College was evacuated to Cam bridge, very little room space could be allocated for research purposes. At the same time the assistants and laboratory attendants were almost wholly occupied in class preparation and had no time to spare to help with research. In 1942 the Physiology block of the London buildings was gutted by fire and all the author’s research equipment, books, journals and reprints were destroyed. The apparatus thus destroyed was almost impossible to replace at that time. The position, so far as apparatus is concerned, has changed recently for the better, as a special instrument has now been constructed, which has shown itself to be suitable for the tasks for which it was designed. This is described in Part X. I would like to thank my colleagues; those in the Cambridge laboratories; those evacuated with us from London; and particularly those who belong to Bart’s. Without their co-operation and encouragement the experiments described in these pages could never have been done at all.

In my previous paper I dealt with the action of the poison of the Sea snakes as far as it was possible to examine it under the conditions of work in Calcutta, and reserved the consideration of certain questions until I was able to test them with the aid of a well-equipped laboratory. This I have now been able to do in the Physiological Laboratory of the London University, by the courtesy of Dr. A. D. Waller, with results which appear to be worthy of being placed on record in a further paper.

In a former paper ( “ Proc. Roy. Soc.,” vol. 33, p. 462) we laid before the Society the results of a series of experiments by which we had endeavoured to ascertain accurately the differences in the duration of the latent period of contraction of skeletal muscle (frog’s gastrocnemius) which could be brought about by varying the following influences :— 1. The weight of load. 2. The mode of applying weight (supported or unsupported), 3. The strength of stimulation. 4. Temperature. 5. Fatigue. We have since been engaged in determining the relative duration of the latent periods of different skeletal muscles of vertebrate animals. Besides several muscles of the Lana temp., we have examined some from the toad, tortoise, small mammals, and birds. In this paper, which is intended to be a continuation of the one above referred to, we beg leave to lay before the Society the results of these experiments and our general conclusions.

1. In preceding papers of this series it has been shewn that the phenomenon of “primary facilitation” of a cortical motor flexion-point lasts for a comparatively short time when stimuli of liminal strength are used. It may, however, occur when the stimuli are of sub-liminal value—as is well known. 2. In a similar manner facilitation of the sub-cortical projection mechanism is also demonstrated in these papers. 3. It has also been shewn that after the primary facilitation of a cortical flexion-point the excitability of other similar flexion-points may be raised —termed here the phenomenon of “secondary facilitation.” 4. The “secondary facilitation” of a less excitable cortical flexion-point after “primary facilitation” of a more excitable flexion-point does not occur after the freezing (and subsequent thawing) of the former point. It may, however, still be present for other less excitable (unfrozen) points which are further removed than the frozen point from the point which is directly facilitated. This shews that the phenomenon is not one due merely to “spread” of the electric current. 5. The “secondary facilitation” of a less excitable point by the “primary facilitation” of a more excitable one is not obtained after a cut in the cortex (and underlying white matter) which is placed between the two points with its plane perpendicular to the line joining them. This shews that the phenomenon of “secondary facilitation” is not solely conditioned by the facilitation (during the “primary facilitation” of the more excitable point) of a lower motor mechanism common to both points. It must be conditioned through association fibres at the cortical level. 6. If this is the case it is a question whether the apparent “secondary facilitation” of a point is conditioned by a direct action upon it of the point which is “primarily facilitated” or by an increase in the effect of the direct action of the first point upon the second (which is exhibiting “primary facilitation”). In either case the phenomenon is conditioned by the action of association fibres, and in either case there is probably a double action between the two points. 7. In the present paper the phenomenon of “post-central activation” is described. After the “primary facilitation” of a motor flexion-point a neighbouring point on the post-central cortex may respond with a similar motor reaction to electric stimulation. 8. This phenomenon of “post-central activation” is in many ways like the “secondary facilitation” of a motor point. It is not usually obtained after the freezing of the post-central point, nor after a longitudinal lesion set between the post-central point and the motor flexion-point, and with its plane perpendicular to the line which joins them. It is therefore probably a physiological phenomenon and not due to “spread” of current; and if so it is probably conditioned by association fibres between the two points, and not by the facilitation by the motor point of a lower motor mechanism common to them both. 9. But just as the phenomenon of “secondary facilitation” of a less excitable motor point by the “primary facilitation” of a more excitable motor point may probably in part be conditioned by the facilitation of a lower motor mechanism common to them both, so in the case of the post-central point there is some evidence which seems to point to a similar occurrence in certain circumstances. If this is the case it seems to shew that the post-central mechanism may act on lower mechanisms by means of its own projection fibres, and not only through the “motor” mechanism in the pre-central convolution. 10. Nevertheless it is shewn that the phenomena both of the “secondary facilitation” of a cortical motor point and the “activation” of a post-central point are conditioned at the cortical level. This for the first time demonstrates a phenomenon of “facilitation” in the cortical mechanism itself, after exclusion of the possibility of its location in a common lower mechanism through which the “motor” centres in the cortex act. 11. In the conclusions of this paper these different phenomena are considered in their bearing upon the problem of cortical localisation of function.

Recent investigations by A. V. Hill (1), Meyerhof (2), Doi (3), and others have made it evident that the heat liberated and tension developed by skeletal muscle during contraction varies for single maximal stimuli as well as for short tetani with the initial passive tension of the muscle, increasing to a point as the initial tension is raised, and then decreasing as the initial tension is raised still further. The mechanism by which this adaptation to differing mechanical conditions is brought about remains as yet obscure. As it seemed possible that a study of the electric responses of muscle subjected to differing mechanical conditions might throw some light upon the question, the following experiments were undertaken. A review of the previous investigations upon this subject has recently been given by Forbes, Ray and Hopkins (4, 1923) in their paper on the effect of tension on the action current of the twitch.

Denny-Brown (1929) and Adrian and Bronk (1929) have described rhythmic discharges from the single motoneurones of extensor muscles during repetitive stimulation of a contralateral afferent nerve. When the stimulation is not too infrequent, e. g. , when more than 10 a second, the rhythm of this reflex discharge bears no direct relation to the rhythm of the stimulation, but within limits it varies with the intensity of the reflex stimulus, which in turn is dependent on both the rate and the strength of the stimulation. Somewhere in the reflex centre the reflex stimulus gives rise to the rhythmic discharge characteristic of the reflex response. This paper describes an investigation into conditions underlying the production of such a rhythmic discharge from a motoneurone. A preliminary account of some of the experimental work has already been published (Eccles and Hoff, 1931).

In the two preceding papers (Bishop, Burke & Davis, 1962 a, b) we have described the responses of single optic tract fibres, lateral geniculate cells and optic radiation axons to orthodromic and antidromic stimulation. In these papers also we discussed the part played by the type of electrode in determining the character of the response, the changes that occur in the responses with time and the wave form of unit responses from axons. In the present paper we provide an interpretation of the wave form of the extracellular responses of single cells in the dorsal nucleus of the lateral geniculate body (LGN) of the cat. Although the wave form of intracellular responses has been discussed extensively, much less attention has been paid to the extracellular wave form. However, there have been valuable discussions by Svaetichin (1951, 1958), Tasaki, Polley & Orrego (1954), Fatt (1957a, b), Hakansson (1957), Freygang (1958), Freygang & Frank (1959) and Murakami, Watanabe & Tomita (1961). From the experimental point ofview we have endeavoured to analyse the wave form by splitting it into its separate components. The results suggest; that extracellular recording may reveal information not available from intracellular records. In view of the increasing use of implanted electrodes, further detailed study is very desirable (cf. Nelson, Frank & Rall, 1960). METHODS

As a step preliminary to some observations on the reflex functions of the spinal cord of the Monkey, I have attempted to make a rather detailed examination of the distribution of the efferent and afferent roots of each spinal nerve, especially in the lower half of the body of that animal. I have recently published some experimental notes on the arrangement of some motor fibres in the lumbo-sacral plexus, and the present paper deals chiefly with the distribution of the afferent fibres of the roots. Previous Observations. In the researches which have had for their subject the peripheral distribution of the posterior roots of the spinal nerves, the plexuses of the Mammalian fore limb have been more studied than have those pertaining to the hind limb. With the exception of the five experiments extant by L. Turck (1856), there seem no experiments on the cutaneous fields of the afferent spinal roots of the Mammalian bind limb previous to my own. This fact may lend interest to observations, especially on so high a type as the Monkey, and I take this opportunity of expressing my thanks to the Royal Society for pecuniary aid, placing that somewhat expensive laboratory animal within my reach.

The ability of certain organisms, including notably the Mollusca and lower Vertebrata, to respond to their surroundings by appropriate pigmentary changes has long been familiar to biologists; it has been recognised for more than half a century that a special type of effector organs (chromatophores, melanophores, etc.) are actively instrumental in producing such changes, and that, in Vertebrates at least, pigmentary response is partially controlled through the nerves by stimuli received from the organs of vision. During the past two decades it has been shown that the reactions of the pigment cells to stimuli simulate those of other effector organs, especially as regards their responses to certain internal secretions. That a fuller understanding of their properties might prove of service to practical aspects of physiology, as well as the key to a knowledge of “colour adaptation,” was realised by Lister, who concludes his paper on the cutaneous pigmentary system of the Frog (1858) with the following comment: “The pigmentary system also promises to render good service in toxicological enquiry. Hitherto in experiments performed on animals with that object attention has been directed chiefly, if not exclusively, to the effects produced upon the actions of the nervous centres, the nerves, and muscles. In the pigment cells we have a form of tissue with entirely new functions, which, though apparently allied to the most recondite processes, yet produce very obvious effects… Such experiments are so readily performed, and the effects produced are so obviously indicated by the changes in colour of the integument, that I venture to recommend this method of investigation to those who are occupied in studying the action of poisons. …” A considerable literature, which has been reviewed too thoroughly and recently to merit an extensive epitome here, bears witness to the intricacy of the mechanism which underlies pigmental response in Fishes, Amphibia, and Reptiles; and very little work has been done on Molluscs in this connection. It can be safely asserted that as many distinct types of chromatophores are already known as there are different sorts of other effector organs whose properties have been studied. Hence it is obvious that, apart from the intrinsic interest presented by the phenomenon of colour change, a study of the properties of this series of effectors invites consideration in relation to a fuller understanding of the rôle played respectively by the character of tissue and the nature of its nerve supply in the local action of drugs. The research, of which this preliminary communication contains an initial account, of the response of Amphibian melanophores to pituitary extracts, has been approached with both these objectives in view. For present purposes it will suffice to recapitulate briefly what has already been achieved in relation to the endocrine factors in pigmental response.