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Background and purposeEpilepsy is most common in lower-income settings where access to electroencephalography (EEG) is generally poor. A low-cost tablet-based EEG device may be valuable, but the quality and reproducibility of the EEG output are not established.MethodsTablet-based EEG was deployed in a heterogeneous epilepsy cohort in the Republic of Guinea (2018-2019), consisting of a tablet wirelessly connected to a 14-electrode cap. Participants underwent EEG twice (EEG1 and EEG2), separated by a variable time interval. Recordings were scored remotely by experts in clinical neurophysiology as to data quality and clinical utility.ResultsThere were 149 participants (41% female; median age 17.9years; 66.6% ≤21years of age; mean seizures per month 5.7±SD 15.5). The mean duration of EEG1 was 53±12.3min and that of EEG2 was 29.6±12.8min. The mean quality scores of EEG1 and EEG2 were 6.4 [range, 1 (low) to 10 (high); both medians 7.0]. A total of 44 (29.5%) participants had epileptiform discharges (EDs) at EEG1 and 25 (16.8%) had EDs at EEG2. EDs were focal/multifocal (rather than generalized) in 70.1% of EEG1 and 72.5% of EEG2 interpretations. A total of 39 (26.2%) were recommended for neuroimaging after EEG1 and 22 (14.8%) after EEG2. Of participants without EDs at EEG1 (n=53, 55.8%), seven (13.2%) had EDs at EEG2. Of participants with detectable EDs on EEG1 (n=23, 24.2%), 12 (52.1%) did not have EDs at EEG2.ConclusionsTablet-based EEG had a reproducible quality level on repeat testing and was useful for the detection of EDs. The incremental yield of a second EEG in this setting was ~13%. The need for neuroimaging access was evident.

WOS: 000442229500021, PubMed ID: 30101073, Background: In infants with phenylketonuria (PKU), dietary management is based on lowering and titrating phenylalanine (Phe) intake from breast milk or standard infant formula in combination with a Phe-free infant formula in order to maintain blood Phe levels within target range. Professionals use different methods to feed infants with PKU and our survey aimed to document practices across Europe. Methods: We sent a cross sectional, survey monkey (R) questionnaire to European health professionals working in IMD. It contained 31 open and multiple-choice questions. The results were analysed according to different geographical regions. Results: Ninety-five centres from 21 countries responded. Over 60% of centres commenced diet in infants by age 10 days, with 58% of centres implementing newborn screening by day 3 post birth. At diagnosis, infant hospital admission occurred in 61% of metabolic centres, mainly in Eastern, Western and Southern Europe. Breastfeeding fell sharply following diagnosis with only 30% of women still breast feeding at 6 months. 53% of centres gave pre-measured Phe-free infant formula before each breast feed and 23% alternated breast feeds with Phe-free infant formula. With standard infant formula feeds, measured amounts were followed by Phe-free infant formula to satiety in 37% of centres (n = 35/95), whereas 44% (n = 42/95) advised mixing both formulas together. Weaning commenced between 17 and 26 weeks in 85% centres, >= 26 weeks in 12% and < 17 weeks in 3%. Discussion: This is the largest European survey completed on PKU infant feeding practices. It is evident that practices varied widely across Europe, and the practicalities of infant feeding in PKU received little focus in the PKU European Guidelines (2017). There are few reports comparing different feeding techniques with blood Phe control, Phe fluctuations and growth. Controlled prospective studies are necessary to assess how different infant feeding practices may influence longer term feeding development., Vitaflo, We thank Vitaflo for supporting the publication cost of this paper.

Sir, Renal papillary necrosis is a well-described entity on intravenous pyelogram (IVP) and CT urogram in both the adult and pediatric populations [1–3]. However pediatric renal papillary necrosis is less frequently encountered, particularly on magnetic resonance urogram [4–6]. Indeed, to the best of our knowledge renal papillary necrosis has yet to be described on MR urogram. We present a case of renal papillary necrosis demonstrated by MR urogram in a child with previously undiagnosed sickle cell trait. A 17-year-old previously healthy African-American girl presented to our institution with a 3-day history of gross hematuria. Her medical history was unremarkable except for recent streptococcal pharyngitis. After 2 months of extensive and inconclusive evaluation, including laboratory analysis, renal US, and a renal biopsy, the hematuria persisted, with hemoglobin decreasing to 4 g/deciliter. The girl was subsequently evaluated by cystoscopy, which demonstrated hemorrhage from the left ureteral orifice. Retrograde pyelogram and cystoureteroscope showed irregularity of the left upper pole papillary urothelium (Fig. 1). At this point, the pediatric urologist was suspicious but not confident of the diagnosis of renal papillary necrosis. Symptoms persisted, so MR urography was performed. MR urogram demonstrated classic changes of bilateral papillary necrosis (Fig. 2). Given these findings, a hemoglobin electrophoresis led to the diagnosis of sickle cell trait. The girl was placed on aminocaproic acid with cessation of hematuria. Imaging of renal papillary necrosis, which is most commonly caused by sickle cell disease and nonsteroidal anti-inflammatory medications in the pediatric population, is well documented within the radiology literature, with Praetorius first describing its radiologic appearance in 1937 [2]. Classically, intravenous pyelogram has been the examination of choice. From its appearance on intravenous pyelogram, multiple classic radiographic signs have been elucidated, e.g., ballon-tee, lobster claw, and signet ring. Recently several authors have demonstrated the imaging appearance and diagnosis of renal papillary necrosis in adults using CT urography [3]. However, given the use of iodinated contrast agent and the radiation dose of both CT and intravenous pyelogram, alternative imaging modalities are helpful for pediatric imaging in suspected renal papillary necrosis. In 1995 Rothpearl et al. [6] reported the techniques and application of MR urography in the depiction of the kidney and bladder pathology. One patient included in this study population had pathologically proven renal papillary necrosis. However, the authors did not elucidate whether the changes of renal papillary necrosis were demonstrable on MR urogram [6]. In a subsequent invited commentary, Hattery and King [7] called into question the utility of MR urogram in the detection of papillary necrosis given the resolution requirements for depicting the subtle changes of renal papillary necrosis at the caliceal and forniceal levels [7]. The authors did J. Schroeder Medical University of South Carolina, College of Medicine, Charleston, SC, USA

Seismic data contain a vast amount of information regarding different properties of the imaged geology. Unravelling the disparate types of information to produce an accurate and detailed subsurface model is a primary purpose of seismic interpretation. To aid this task, a wide range of volumetric seismic attribute computation techniques have been developed. Seismic attributes are designed to measure, extract, or enhance specific characteristics of the data so information regarding different aspects of geology can be examined independently. However, an accurate and comprehensive interpretation can seldom be obtained from analysis of individual attributes in isolation; rather, it is necessary to consider information from different attributes simultaneously. Multiattribute analysis can be formulated as a process of examining a joint attribute space where there is often a degree of correlation between the bases.

Introduction Abstract presentations at scientific meetings allow rapid dissemination of novel research and enables peer review before submission for publication. The percentage of abstracts that achieve full publication, however is variable ranging between 11–78% from other medical specialty meetings. This study evaluates the conversion rate of abstracts presented at the BSG annual meeting, and comperes the outcome from this national meeting with another internationally recognised gastrointestinal meeting (UEGW). Methods All abstracts presented at the BSG between 1994 and 2008 were reviewed in Nov 2012. UEGW meeting abstracts between 2009 and 2011 were reviewed in October 2014. Review dates for both the BSG and UEGW abstracts were at least 3 years post the last meeting evaluated, which is a previously reported upper limit timescale for subsequent full publication. PUBMED and EMBASE databases were reviewed using cross-referencing of first author, senior author and at least one key word from the abstract title. Abstracts and possible full publications were then examined in tandem to ensure they represented the same study. Abstracts that were withdrawn were excluded from the study. In addition to publication rates, data was collected on lag time to publication and journal impact factors. Statistical analyses were performed using contingency tables and chi squared statistics for categorical data using SPSS version 20.0. Results Over a 15 year period (1994–2008) the conversion rate of BSG abstracts to full publication was 33.4% (2273/6798, mean impact factor of published journal = 3.8). The mean lag time until publication was 23 months, with service development abstracts having the lowest conversion rate of 6.9% (8/116). Of the 6560 abstracts presented at UEGW meetings between 2009–2011, 31.0% (2033/6560) went on to full publication in indexed journals (mean impact factor = 3.93). The mean lag time between UEG abstract presentation and full publication was 16 months. The conversion rate of BSG abstracts is broadly comparable to UEGW, however it did achieve a statistically significant difference (33.4% vs.31.0% p = 0.003). Conclusion This study demonstrates that the BSG compares favourably to another internationally recognised gastroenterology meeting with regards to the outcomes of its abstracts. Findings from this work provides reassurances to researchers that submission to the BSG annual meeting is worthwhile, and that the peer-review process provided increases the likelihood of success in achieving subsequent full publication. Disclosure of Interest None Declared

The author addresses the diagnosis of seizure disorders by discussing clinical features of the different types of seizures, including generalized tonic-clonic, absence, myoclonic, partial complex seizures, and non-epileptic or “pseudoseizures.” She also discusses the use of appropriate laboratory tests, electroencephalography, computed tomography, magnetic resonance imaging, and positron emission tomographic scanning. The rationale of and approach to treatment of these conditions with some of the common anticonvulsant drugs (phenytoin, carbamazepine, valproic acid, phenobarbital, and primidone) is provided.

B012 RGB Visualisation Based Delineation of Geological Elements from Volumetric Spectral Decomposition of 3D Seismic Data S.J. Purves* (Foster Findlay Associates) J. Henderson (Foster Findlay Associates) & C. Leppard (Hydro) SUMMARY The paper describes a novel set of multi-channel RGB 3D visualisation and GeoBody detection and delineation techniques that form the basis of a true spectral decomposition based volume interpretation workflow developed as part of a research and development collaboration between ffA and Hydro. EAGE 69 th Conference & Exhibition — London UK 11 - 14 June 2007 Introduction The spectral content of recorded seismic data is dependent on the

The safety of biotechnological products used for medicinal products is addressed by EU council directives. The general principles and the regulatory framework for the handling of new drug applications within this areas are described both with respect to benefit/risk evaluation, quality assessment, preclinical safety and efficacy testing.

Corpus Callosum Section (CC Section) has attracted renewed interest in recent years as an option for surgical treatment for patients with medically intractable seizures who are not eligible for resective surgery. A variety of seizure types have been considered for treatment and this topic reviewed extensively elsewhere (Purves 1991, Spencer 1988, Gates 1992). There is some agreement emerging that specific types of generalized seizure patterns such as atonic or tonic drop attacks respond well to CC Section. The application of this procedure for complex partial seizures is still poorly understood. Much of the interest in CC Section for CPS has centered on those of presumed frontal origin but the extent of documentation of this assumption is often unclear.

Rationale Measurement of exposure to fungi continues to be of interest as an aid in the diagnosis of respiratory allergies. Settle or gravity plates, which are commonly used, provide little information about actual concentrations of fungal spores in the air. The well-known Andersen sampler is too expensive to send home with patients. We have developed and tested the Biocassette, a disposable version of the Andersen sampler. Methods We have conducted 50 paired tests comparing the Biocassette with the Andersen. We compared total recoveries and recoveries of Penicillium graphically and statistically following transformation to approximate normality. Total recoveries were log-normally distributed, and transformed data from the two samplers was linearly related (y=0.6433x+2.083, R2=0.4748). Results Paired T-tests on the log-transformed data failed to reject the null hypotheses (no difference between the two samplers). Penicillium data were subjected to a square root transformation to approximate normality. These transformed data were linearly related (y=0.7788x+2.2018, R2=0.5495, and no significant differences were revealed in the Paired T-Test. Conclusions The Biocassette appears to produce results that are comparable to the Andersen sample both for total culturable fungi and for small spores as represented by Penicillium. The sampler should be a valuable addition to the allergist's environmental control arsenal.

The use of automated mapping/facilities management, geographic information systems (GIS), and computer aided design-drafting (CAD) technology within the water industry was surveyed by the AWWA Computer Assisted Design Committee. Of the 270 respondents, only 20 percent indicated that they had no involvement in computerization in these areas. In addition to standard applications such as engineering drafting and facilities mapping, utilities are using raster data for document imaging and interation of raster and vectorized data and developing interfaces between GIS and other systems such as supervisory control and data acquisition, customer billing, and hydraulic models

SUMMARYMultimodality evoked potentials testing including PVEPs, SEPsand BAEPs was done in 112 patients who were known or suspected to have multiple sclerosis. The incidence of abnormal evoked potential findings in each of these systems was considered in patients in the different diagnostic categories of M.S. Results were also evaluated with respect to the presence of abnormal clinical visual, somatosensory, or brainstem signs. The PVEP was found to be the most frequently abnormal even in patients without clinical involvement in the visual system (45% of patients with definite, probable, or possible M.S.), the SEP was less frequently abnormal in the absence of clinical signs (35% in patients with M.S.), and the BA EP showed the lowest frequency of abnormalities in patients without brainstem signs (14% in patients with M.S.). Combining the three types of evoked potentials significantly increased the percentage of M. S. patients having abnormal findings, compared to any of these tests alone, with 97% of “definite” M.S. patients, 86% of “probable” M.S. patients and 63% of “possible” M. S. patients having at least one of these EP tests abnormal.

1. Parallel recordings have been made of the cervical sympathetic and carotid body chemoreceptor activity in the anaesthetized cat. 2. The sympathetic activity remains remarkably constant while the chemoreceptor activity is varied by changes in the blood gas tensions of relatively short duration. 3. Changes in intrathoracic pressure by obstruction to the airway or thoracic compression were associated with changes in the activity of both nerves. 4. It is likely that, under normal conditions, the sympathetic nervous activity provides a stable vasomotor tone within the carotid body.

1. In the sinus nerve of mature foetal sheep (120-147 days gestational age) three types of nerve activity have been demonstrated: (a) baroreceptor afferent, in which the nerve activity was synchronous with the pulse pressure wave and which followed pressure changes in the carotid sinus including those caused by compressing the umbilical cord. The discharge of nine out of twelve baroreceptor afferents increased with sympathetic stimulation, (b) a subtype of (a) in which there was irregular activity from pressure receptors which most probably represented baroreceptors discharging at or about threshold, and (c) in the older foetuses (130-147 days), there was activity which was unaffected by changes in carotid sinus pressure, Pa, O2 or NaCN but which increased in discharge rate with compression of the umbilical cord or with stimulation of the cervical sympathetic; this activity then increased with injection of NaCN and was thus identified as chemoreceptor in origin. In addition, a pathway originating in the cervical sympathetic and which passed through the superior cervical ganglion was demonstrated by evoking a compound action potential on stimulation of the preganglionic cervical sympathetic nerve. 2. Recordings from pre- or post-ganglionic cervical sympathetic nerves showed that spontaneous activity was present and increased when the umbilical cord was compressed. 3. These results suggest that the carotid body chemoreceptors in the foetus are relatively insensitive to chemical changes and that, in their activation at birth, the sympathetic could be involved. Possible neural pathways and the mechanism of activation are discussed.

1. Afferent activity was measured in the vagus nerves in sixteen foetuses within 2-3 days of natural term and in two foetuses 130 and 135 days gestational age, exteriorized by hysterotomy from seventeen ewes given either a spinal anaesthetic (ten) or pentobarbitone sodium (seven).2. Activity from aortic chemoreceptors was observed which increased in rate with foetal hypoxia, NaCN or nicotine and temporary occlusion of the umbilical cord or veins. Activity was abolished or reduced with saline equilibrated with air.3. Activity from baroreceptors was observed which was synchronous with the arterial pulse and which followed changes in arterial pressure.4. Activity designated as arising from stretch receptors in the lungs or lower airways was observed which consisted of a regular discharge at 15-45 impulses sec(-1), which varied with intra-tracheal pressure, which increased with negative intrathoracic pressure generated by spontaneous respiratory movements, which, when the umbilical cord was occluded, at first increased in rate and then fell to zero at or about the occasion of the first breath. After breathing had been established, activity assumed the rhythmical pattern and showed evidence of slow adaptation of receptors seen in the adult. This activity was frequently modulated by the heart beat and after breathing had started it was reduced when carbon dioxide was raised.5. Respiratory movements with a frequency of 10-20/min occurred spontaneously in foetuses from ewes given a spinal anaesthetic and were associated with a modulation of the stretch receptor discharge. They could be induced by withdrawing fluid from the trachea and so lowering both intra-tracheal pressure and receptor discharge and were abolished by raising intra-tracheal pressure. These changes were abolished by sectioning the vagi just caudal to the nodose ganglion.6. These results indicate that there are excitatory and inhibitory pathways in the vagus nerves which are active in the foetus and which may well be concerned with the limitation of respiratory movements of the foetus and the onset of maintained respiration at birth.

1. The respiratory response to inhaled CO(2) was measured in twenty unanaesthetized new-born lambs aged 4 hr-10 days. Measurement of resting arterial pH, P(CO2) and plasma bicarbonate showed a non-respiratory acidosis immediately after birth which was corrected in the first 24-28 hr: thereafter, the acid-base pattern was of a compensated respiratory alkalosis.2. When CO(2) was added to the inspired gases and resting arterial oxygen tension (P(a), (O2)) was controlled, the average increase in minute ventilation (V) was 0.075 l.min(-1).kg(-1).mm Hg, P(a), (CO2) (-1) and duplicate responses in the same lamb differed by 6-22.5%.3. The slope of the V/P(a), (CO2) line (S) varied inversely with P(a), (O2). In one lamb, severe hypoxia (P(a), (O2) = 21 mm Hg) caused a marked depression of the slope.4. Neither the slope S nor the horizontal intercept B of the lines was related to the age of the lamb. B was not related to pH(a) and only slightly affected by acute hypoxia. B was related to arterial [HCO(3) (-)] and values for both were reduced with the acid-base disturbances seen in the first 10 days after birth. Evidence was given which suggested that the response of the new-born lamb to inhaled CO(2) was similar to that of man acclimatized to a P(a), (O2) of 70-75 mm Hg.5. In the lightly anaesthetized lamb, bilateral section of the sinus nerves caused a small reduction in the sensitivity to inhaled 5% CO(2) in air, an increase in the respiratory lag and a reduction in the rate at which V increased.6. It was concluded that, in the new-born lamb, the carotid chemo-receptors are involved in the response to inhaled CO(2) and that hypoxia potentiates this response.

1. Carotid body blood flow (c.b.f.) and carotid arterial-carotid body venous oxygen (A-V O(2)) difference were measured and carotid body oxygen consumption calculated in twenty-six cats anaesthetized with pentobarbitone sodium, paralysed with gallamine triethiodide and ventilated mechanically.2. With the sinus nerves intact and with blood gas tensions and carotid sinus pressure within physiological limits, section of either the pre- or post-ganglionic cervical sympathetic nerve on the same side caused an average rise in c.b.f. of 9.2 mul./min, in A-V O(2) difference of 0.09 ml./100 ml. and in carotid body oxygen consumption of 0.075 mul./min.3. When the pre- or post-ganglionic cervical sympathetic nerves were stimulated, c.b.f. and A-V O(2) difference fell. The fall in c.b.f. was enhanced at high P(a, CO2); the fall in A-V O(2) difference and in calculated oxygen consumption was enhanced at low mean arterial pressure (M.A.P.) or P(a, O2).4. Following sympathectomy, a reduction of M.A.P. at constant P(a, O2) and P(a, CO2) caused a fall in c.b.f. and a commensurate rise in A-V O(2) difference so that carotid body oxygen consumption remained approximately constant.5. When P(a, O2) was altered over the range 35 to > 400 mm Hg, or P(a, CO2) over the range 27-70 mm Hg at constant M.A.P., c.b.f. changed by amounts which were similar to those observed when the sympathetic nerves were intact and A-V O(2) difference changed in the opposite direction so that carotid body oxygen consumption similarly remained constant.6. Comparison of these results with those observed when the sympathetic nerves were intact indicates that the sympathetic nerves exert a vasoconstrictor effect upon carotid body blood vessels over a wide range of blood gas tensions and arterial pressure and that they also tend to diminish the rate of carotid body oxygen consumption. The mechanisms which may be involved in this regulation are discussed.

Blood gas tensions, pH and intravascular pressures have been measured at various sites in 22 foetal sheep of gestational age 110–147 days. Umbilical venous oxygen tension did not change significantly with age. The mean pulmonary artery pressure always exceeded that in the aorta and this pressure gradient did not change with age. By contrast the umbilical arterio-venous pressure gradient increased with age. When the ewe breathed room air, the oxygen difference between uterine artery and umbilical vein was 43–62 mm. Hg. When the ewe breathed 100 per cent 02 umbilical venous P02 rose by 4–15 mm. Hg and umbilical venous pH fell by 0·04–0·07 pH units. There were no consistent changes in foetal heart rate or blood pressures. When the ewe breathed 10 per cent O2 in N2, umbilical venous P02. fell by 7–14 mm. Hg, mean pressures in pulmonary artery and aorta and the pulmonary artery/aortic pressure gradient increased as did the size of the right to left shunt across the ductus arteriosus. Heart rate invariably increased. The oxygen saturation difference between ascending and descending aorta was maintained or increased. These results suggest (1) that factors other than a diffusion barrier to oxygen are responsible for the maternal/foetal oxygen gradient and (2) that, with maternal hypoxia, there is a redistribution of blood flow in the foetus so that as high a tissue P02 as possible is maintained in coronary and cerebral circulations.

1. Twenty-seven unanaesthetized new-born lambs, 6 hr-10 days old, responded to two levels of inspired oxygen, 125 and 110 mm Hg (alveolar CO(2) being controlled) with a sustained increase in minute ventilation (V), a small increase in heart rate and a less consistent rise in systemic blood pressure.2. An increase in V was observed when arterial oxygen tension (P(a), (O2)) had fallen by 6-15 mm Hg. There appeared to be no fixed threshold of P(a), (O2) at which ventilation started to increase.3. The increase in ventilation caused by these levels of hypoxia was significantly and directly related to the age of the lamb and to its control alveolar CO(2).4. More severe hypoxia caused a progressive increase in V until P(a), (O2) was about 25 mm Hg when respiration failed. This increase at P(a), (O2)25 mm Hg was markedly potentiated when alveolar P(CO2) (P(A), (CO2)) was increased and abolished after bilateral denervation of the carotid chemoreceptors.5. Significant (10%) left-to-right shunts were found in ten out of twelve lambs lightly anaesthetized with pentobarbitone sodium, breathing air. Hypoxia diminished the left-to-right pressure gradient largely by its pressor effect on the pulmonary circulation. When inspired O(2) tension (P(I), (O2)) was 70 mm Hg, all seven lambs studied showed a reversal of the pressure gradient and evidence of right-to-left shunts (11-42%) across the ductus arteriosus.6. The implications of these findings have been discussed with reference to previous studies of the new-born response to hypoxia and it is concluded that the peripheral chemoreceptors are fully active at birth and in the new-born period.

Crandall’s difficulty (this vol) is this. The hypothesis proposed by Hill et al (1973) and Forster and Crandall (1975) predicts that as blood flows through the pulmonary capillaries and CO2 is lost, a disequilibrium between [H+] in plasma and [H+] in the red cell will be set up because the dehydration reaction will be catalyzed in the red cell but not in plasma. They further predict that the resolution of this disequilibrium will be reflected by a slow rise of pH and \({{\text{P}}_{C{O_2}}}\) in post pulmonary capillary blood. In favour of this hypothesis is the observation that pH does, in fact, rise in pulmonary post-capillary blood (Hill et al., 1977; Bidani and Crandall, 1978) but against the hypothesis is the compelling evidence that carbonic anhydrase is available to plasma as blood passes through the pulmonary capillaries (Effros et al., 1978; Crandall and O’Brasky, 1978; Hanson et al., 1979). Thus, no H+ disequilibrium should occur. Nor should pH in post-capillary blood change. Yet, it patently does. It is therefore likely that there must be an alternative explanation for the changes in pHa.

SUMMARY:Visual evoked responses (VER) to four geometric shapes (a square, circle, el and omega) were recorded from multiple scalp locations in twelve subjects. Significant differences were found between the occipital VERs to the square and el and between the VERs to the circle and omega. Consistent differences could not be demonstrated between the responses to the square and circle or to the el and omega.The differences between the responses were quantified by three different methods, including measurement of peak latencies and amplitudes, computation of a ratio index called λ, and the performance of discriminant functions derived by Stepwise Discriminant Analysis Program (SWDA) in classifying other single trial responses. The amplitudes (but not the latencies) of a negative peak at approximately 150 msec, and a positive one at 220 msec, latency were found to be different in the pairs of shapes described. SWDA was able to separate these same pairs and classify from 63 to 68% of new trials correctly. The latency points chosen to make up the discriminant functions correlated partly with the and components that were found to be significantly different in amplitude.It is suggested that the VER differences in the earlier part of the wave-form are related to the physical properties of the stimuli, including the contrast densities in the central 1.5° of the visual field and/'or the spatial frequencies contained in the stimuli. Differences demonstrated in later parts of the VERs may reflect differences in symbolic meaning of the stimuli.

Carotid body chemoreceptor afferent discharge was recorded in the sinus nerve of sheep fetuses within a few days of term, exteriorized from ewes given pentobarbitone anaesthesia, and in six newborn lambs, 7-21 h old. Chemoreceptor discharge, defined as such since it was irregular, had no relation to the heart beat and was excited by hypoxia, hypercapnia, H+ and NaCN, was recorded in only 8 out of 20 fetuses. It was abundant in both the newborn lambs and also in fetus carotid bodies studied in vitro. Although electrical stimulation of the sympathetic fibres to the carotid body excited the fetal chemoreceptors and caused a fall in carotid body blood flow, the fetal chemoreceptors still responded to natural stimuli and drugs in both fetus and lamb after the sympathetic pathway had been cut. Further, there appeared to be clear dissociation of chemoreceptor and sympathetic activation shortly after birth. These results confirm and extend earlier studies and they suggest that, although the sympathetic pathway may contribute to chemoreceptor activation at birth, other, possibly more important, factors must be involved. These are discussed.

1. Respiratory responses were measured in forty-seven cats, made decerebrate or anaesthetized with pentobarbitone or chloralose-urethane, to changes in the level of CO2 infused into the inferior vena cava via an external oxygenator circuit or to changes in the volume of venous return or to the inhalation of CO2. 2. No consistent difference was found between the respiratory response to the increase in the level of CO2 infused or CO2 inhaled provided that the volume of venous return during both sets of tests was held constant at normal levels. 3. If the volume of venous return was increased and the level of CO2 infused maintained at levels such that VCO2 did not increase, ventilation increased with a fall in Pa, CO2, a response lying approximately on the isometabolic curve. 4. If the volume of venous return and the level of CO2 infusion were raised together, a spectrum of intermediate respiratory responses was obtained which reproduced all those seen in earlier papers, in muscular exercise or other hypermetabolic states. 5. None of the steady-state respiratory responses was significantly affected by bilateral vagotomy or section of the sinus nerves, though sinus nerve section slowed the responses to infused or inhaled CO2 and they were then less precisely controlled. 6. Additional experiments indicated that where CO2 was infused or inhaled, the effective stimulus to respiration was an increase in mean Pa, CO2 in proportion to the CO2 added and that the respiratory response to CO2 was enhanced by reduced blood volume. How the changes in venous return were sensed and affected respiration, remains unclear. 7. These results may explain why previous workers have obtained exaggerated respiratory responses to the infusion of CO2 and why respiration increases rapidly at the start of exercise and is then maintained at high levels without discernible change in the chemical stimulus in arterial blood.

SUMMARY:Somatosensory evoked potentials (SEPs) were recorded following trigeminal nerve stimulation in 25 normal subjects. Mucosal stimulation of the lip resulted in a reduced stimulus artefact. The three initial peaks, N13, P19, and N30, measured respectively 12.8 ± 0.9 S−3, 19.3 ± 1.4 S−3 and 28.6 ± 1.7 S−3. Blink reflex studies were also performed in most of these subjects. In 41.4% of 29 patients with established or suspected multiple sclerosis, the trigeminal SEP was abnormal. Additional use of the blink reflex raised the overall incidence of trigeminal nerve dysfunction to 51.7%. None of the patients had clinical evidence of fifth nerve involvement either historically or on examination. Four of seven patients with progressive spinal MS and two patients whose only deficit was that of optic neuritis, had abnormal trigeminal SEPs. It is concluded that occult involvement of the pontine fifth nerve structures occurs frequently in MS despite the rarity of corresponding clinical findings. The trigeminal SEP is a useful additional neurophysiological method.