Reports of Societies

1899 BMJ (Clinical Research Edition)  
President, in the Chair. Tuesday, May 23rd, 1899. THE SPJNAL ANIMIAL. PROFESSOR C. S. SHERRINGTON delivered the Marshall Hall Lecture on this subject. He said that Marshall Hall considered the spinal cord to be a series of functional or physiological segments, as distinct from its anatomical segments. The lecturer referred to what he termed the fractionated capacity of the spinal cord, particularly for the maintenance of reflex action in its segments. For instance, in the case of lemulus, the
more » ... e of lemulus, the whole of the nervous system corresponding with brain might be removed without interfering witlh the automatic movements, particularly those of respiration, represented in the spinal cord; co-ordination alone being abrogated. He referred to similar reflexes persisting in the vertebrate cord after its separation from the brain, for example, the wagging movements of the tail in the monkey. A typical spinal segment he defined as consisting of two groups of root cells, the anterior and posterior, the dorsal group containing cutaneous, muscular, and visceral afferent cells, the anterior containing skeletal, vascular, and visceral cells. The peripheral distribution of the cutaneous afferents was zonal in shape, with an overlapping of adjacent areas. The apparent irregularity in this distribution of the sensory fields in the limbs was only apparent, the zonal arrangement being really maintained. He illustrated the limb fields by the striping of the tiger and the zebra. He had been unable to find any spot in the skin of the monkey that was not supplied by two overlapping roots, but the degree of overlapping varied in different parts of the body; for example, part of the pinna of the ear was supplied by three roots, and so was a portion of the hand. The visceral and vascular root cell afferents came from the sympathetic, and the cells themselves were undoubtedly in the spinal ganglion; for example, the tenth root contained contributions from the kidney and the liver. In onie ramus communicans i6o nerve fibres had been counted. The situation of the referred pains investigated by Dr. Head threw light on the actual source of the sensory fibres for any segment. He alluded to Haller's division ot the parts of the body into those which feel and those which do not feel-for example, the liver being an absolutely insensitive organ. In the present day of anaesthetics painful impressions were not in evidence, but reflex changes connected with the blood vessels, particularly changes in blood pressure were observed instead. In respect to the liver no fewer than ten roots had fibres passing from it. The muscular afferents, comprising afferents proceeding from the joints and tendons, were then discussed; the ending of some of the afferent nerve fibres being the muscle spindles, the pathology of which had been investigated by Dr.' Batten. The motor nerve cells of the spinal segment innervated a zone of muscles passing half way round the body. But in the limb plexuses the arrangement was morecomplex, yet by meansof the Wallerian degeneration the same zonal arrangement could be tracked down. Each individual muscle was innervated by more than one nerve root, and particularly the muscles at the periphery of the limbs. The different aflerent nerve fibres from a muscle always corresponded with the segmental cells of the motor neuron to the muscles. He illustrated this canon by the nerve mechanism of the knee-jerk, both motor and sensory central mechanisms being in the same segment or segments. The intraspinal position of these elements was clear as regards the dorsal or afferent cells, being the intervertebral ganglion, but the grouping of the ventral or efferent cells was not so obvious. The motor filaments drained the particular level of the cord at which they took their exit, showing that their intraspinal course was horizontal. There was the passage of fibres of one filament to several muscles, that is, each muscle had motor cells scattered through a long extent of the spinal cord If the central end of a divided posterior root were stimulated-for example, in the dorsal region-the first contraction with a minimal stimulus appeared in its own zonal segment. [MAY 27, 1899. The first to reply were the upper portions of some of the abdominal muscles. The muscles of the opposite side were not affected until very late, but on increasing the stimulus there was a spread to the musculature of the adjacent segments rather earlier towards the tail than the head side, as shown by Dr. Page May, there being but a slight barrier of resistance between each pair of segments. In regard to the muscles of the limbs, on stimulating any one of three afferent filaments a reflex contraction could be made to appear in one corresponding muscle. That there was a certain amount of overlap in the visceral afferents he illustrated by the nerve supply of the iris, but the subject as a whole was at present too speculative to allow of discussion. Many of the spinal reflexes were said to be purposive, but the purpose of any reflex referred alone to the segment of the body with which it was connected and not to the individual. The spinal cord might be looked upon as the representative of the organic functions of the body and apart from the influence of the special senses. The cutaneous sense represented in the spinal cord had several principal foci-for example, stimulation of the tip of the ear, the tip of the tail, the perineum, the palm and sole evoked a disproportionate amount of movement as compared with the other parts of the skin. He threw out the suggestion that there was a rudimentary muscular sense located in the spinal cord. No spinal reflex movement was ever an inco-ordinate movement. If amphioxus were divided into three parts, each portion swam the right side up, and if inverted corrected its position; the amputated ray of a starfish, if placed on its back, rectified its position-facts suggestive of a kind of topical consciousness. In conclusion, he referred to the condition of spinal shock. A paralysis from this cause in the monkey might be produced in profound degree, but this did not obtain in the invertebrate animals. It did not, however, seem to be more intense in the monkey than in the frog, if gauged by the vesical and anal functions, but there was an enormous difference in the implication of the skeletal muscles, suggesting that evolution had modified these muscles rather than those of the organic functions. cussing the etiology of pathological dilatation of the heart he alluded to dilatation under physiological conditions of the circulation. Reference was made to the work of Roy and Adami, Starling, and others, with a view to showing that, whilst within certain narrow limits the dilatation induced by some exertion might be a mechanical advantage in relation to the ventricular output, these limits were soon passed and the dilatation was then an evidence of heart fatigue. This might be induced prematurely by the strain to which the heart muscle was subjected being excessive, or by the heart muscle itself being out of condition, but was especially easily produced if both factors were combined, and under such circumstances a condition which was in the first instance physiological might very readily pass into dilatation which was definitely pathological. The important principle in relation to dilatation under physiological conditions of the circulation was that the liability to its occurrence depended upon the inter-relation between (i) the element of increased mechanical strain tending to increase of intraventricular pressure; (2) the condition of the myocardium at the time being. In respect to dilatation under pathological conditions, the element of mechanical strain as a factor in its causation was first considered. The principal causes of increased intraventricular pressure were referred to, and it was pointed out that in addition to the primary effects of the increased strain owing to alterations in the physical condition of the heart, certain additional factors had to be considered, more especially the consequences of increase of residual blood in the ventricles, and the effect of tension on a muscular sphere or spheroid like the ventricle. Variations in the coronary circulation and the relation between the blood pressure in the systemic circuit and that in the coronary area must also be borne in mind. Dilatatiom, in the causation of 1276 TnD BU Kwc IX O HARVEIAN SOCIETY OF LONDON. LTh BsR 1 I DICAT JoUv* 12 7 7 which myocardial weakness was the primary and predominant factor, was then considered, reference being made to the dilatation of acute specific diseases, with or without actual myocarditis, to fatty and other forms of degenerative senile myocardial weakness, the dilatation of nervous and general debility, of severe forms of anremia, and that due to toxic causes, such as alcohol and tobacco, and probably also to toxic substances present in auto-intoxication of gastrointestinal origin. The differences in the degree of dilatation from these various centres were discussed, and stress was laid on the fact that in relation to prognosis the degree of dilatation must always be considered in conjunction with the condition of the heart muscle with which the dilatation was associated. Whilst chronic dilatation might be due to increased strain alone, or to primary myocardial weakness alone, in the most severe forms of dilatation both factors were frequently combined and the principle enunciated in connection with physiological dilatation was similarly illustrated in pathologfical dilatation-namely, that the essential point was the inter-relation at the time being between the element of mechanical strain and the condition of the myocardium. Even in cases in which the element of increased mechanical strain was the chief factor in the causation of the dilatation, its late developments were often traceable to the supervention of myocardial changes. The latter part of the paper was devoted to the significance of the dilatation. Just as physiological dilatation (beyond certain narrow limits) was an evidence of heart fatigue, pathological dilatation was an evidence of heart overstrain, past or present, and frequently the precursor of heart failure. In disease. as under physiological conditions, it was broadly true that the heart's power of doing work was in inverse ratio to the degree of dilatation, but the greater the degree of deviation from the comparatively simple conditions of a healthy heart dilated by excessive strain, the less could reliance be placed on the degree of dilatation as, per se, a gauge of the severity of the lesion. In order to estimate with any approach to accuracy the significance of any given case of dilatation, attention must be given to the degree of dilatation, the condition of the myocardium with which the dilatation was associated, its precise etiology (with especial reference to the relation of the cardiac dilatation to the general health, and the relative importance of the mechanical and myocardial factors in its production), the extent to which the dilatation interfered with the work of the heart in relation to the general circulation, and the degree of recuperative power, as evidenced by the course of the case and the effects of treatment. A broad view on lines such as these was essential if the extremes were to be avoided of making too much or too little of any given case of cardiac dilatation. Dr. ALEXANDER MORISON protested against the tendency of many physiologists of the present day to regard the muscular element as the predominant factor in su-tained rhythmical action, and considered that both clinical experience and pathological investigation, rudimentary as the latter still was, pointed to the important role played by the nervous system in such cases. Dr. JOHN BROADBENT considered that the myocarditis which so frequently accompanied endocarditis, and not the actual lesion to the valves, was responsible for the initial dilatation, from which the heart might entirely or only partially recover. Subsequently, as the valves in the process of repair became puckered and deformed by cicatricial contraction of the granulation tissue on their surface, the effects of the valvular lesion became pronounced, and led to fresh-dilatation of the heart, followed by hypertrophy, which coDstituted a measure for estimating the extent of the valvular lesion. lt was important, therefore, not only to enjoin absolute rest after an attack whilst the heart was recovering from the initial dilatation due to accompanying myocarditis, but subsequently to insist on great care and moderation in exercise, at a later period when compensatory changes called forth by the valvular lesior were taking place. Otherwise undue and permanent dilatation with exceEsive hypertrophy might eiisue. Dr. G. A. SUTHERLAND asked whether dilatation was ever preserit without hypertrophy. Dilatation must be either an active or a passive process as regards the cardiac muscle. A G passive dilatation in cardiac failure implied that the blood could be pumped through the arterial and venous systems by the left ventricle in a weakened condition, and yet remain under sufficient pressure to dilate the ventricle. It was difficult to accept such an explanation on physical grounds, as venous engorgement and cardiac syncope would appear to be a more likely result. Active dilatation on the the other hand might be the calling into play of some reserve power in the heart which by greater expansion and more rapid action was enabled to carry on the circulation. As compensation was often fully established under these conditions he thought that dilatation might be looked on as a conservative process, and one not necessarily to be interfered with medicinally or otherwise, although it was recognised that over-action of the heart was present, and that a breakdown must occur in the course of time. Dr. POYNTON agreed with Dr. Sutherland as to the difficulty in many cases of explaining dilatation of the heart upon mechanical considerations. In rheumatism dilatation might be very marked, and the clinical symptoms comparatively slight, whereas in other conditions the clinical symptoms might be very severe and the dilatation slight. Microscopic examination of the heart walls sometimes slhowed extensive myocardial disease with little dilatation and sometimes the reverse. In rheumatism he thought it probable-a view also held by Dr. Lees-that the marked dilatation was dependent upon a special and peculiar action of the rheumatic toxin upon the cardiac muscles. The difficulty and complexity of the question of cardiac dilatation was illustrated by the caee of a young man about 24 years of age, who having been " out of sorts " for some days went for the first row of the season " ir a four-oar to shake it off." On landing after this exeition he vomited, and later in the day was seen by a doctor who found that his heart was extremely rapid, his pulse-i ate being about. 200 to the minute. He was admitted under Dr. Cheadle to St. Mary's Hospital in this condition and died two or three days. afterwards, the heart acting to the end at this extraordinary rate. The necropsy showed mitral valvulitis and old pericarditis. The dilatation was quite moderate. In this case there were two factors: a damaged heart and a mechanical strain, both, one would have thought, tending to extreme dilatation, rather than a condition of tachyeardia with little dilatation. It was important to get a definite idea of the meaning of fibrous changes in the heart wall, for sometimes they were brought forward to account for dilatation and sometimes they were given as an explanation of its absence. Those fibrous clhanges which arose in connection with the vessels were, he thought, essentially reparative, and an evidence of Nature's reaction, however imperfect, to morbid processes. The valve deformities of rheumatism were thus an evidence of reaction to the toxic process rather than evidence of the active effects of the toxmemia. Dr. BEZLY THORNE also spoke. Dr. H. A. CALEY, in reply, remarked that practically we could only estimate alterations in the cardiac nervous. mechanism by noting any alterations in the frequency and rhythm of the heart beat, and by estimating, as far as possible, the amount of conti actile vigour which the heart muscle possessed. In reply to the question as to whether slight degrees of dilatation might not be beneficial, it was pointed out that just as a slight degree of dilatation under physiological conditions might be a mechanical advanitage, so a corresponding degree of dilatation under pathological conditions. might likewise be advantageous, provided t!Nat it was accompanied by sufficient vigour of the heart muscle, with or without actual hypertrophy. This had been referred to in the paper as strictly compensatory dilatation. DISEASES OF MYOCARD1UM. Dr. POYNTON exhibited microscopic specimens illustrating various diseased conditions of the myocardium. The sections were taken through the left ventricle and papillary muscles, and in one case the aoita. They showed the peneral fatty changes that might occur in severe iheumatic morbus cordis, the extreme myocardial disease that might occur in Eome cases of alcoholism, and the severe and active changes that might be found in the heart wall in acute aortitis without demonstrable affection of the coronary veesels. The explanation of the con-INIAY 2 7,. 1899-1 TM B
doi:10.1136/bmj.1.2004.1276 fatcat:xotkmh5wlrf2fj5crzrienhslq