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Causal analysis of molecular patterning at neural plate and early neural tube stages has shown that the central nervous system (CNS) of vertebrates is essentially organized into transverse neural segments or neuromeres and longitudinal zones which follow the curved axis of the brain. The intersection of the longitudinal and transverse patterning processes in the embryonic brain leads to the formation of a checkerboard pattern of distinct progenitor domains called “fundamental morphological units” (FMUs). The topologically invariant pattern formed by the ventricular surfaces of the FMUs of a given taxon represents the “Bauplan” or “blueprint” of the brain of that taxon. The FMUs initially represent thin epithelial fields; during further development they are transformed into three-dimensional radial units, extending from the ventricular surface to the meningeal surface. It is of note that the boundaries of the neuromeres, longitudinal zones, and radial units all strictly adhere to a non-Cartesian coordinate system inherent to the CNS of all vertebrates. The major neural histogenetic processes, including cellular proliferation, radial migration, and differentiation, as well as the formation of grisea (cell masses, nuclei, and cortices), occur principally within the confines of the FMUs, although tangential migration may also take cells to distant sites. Hence, recognition and delimitation of these units is essential for the identification and interpretation of grisea. An outline of the procedure to be followed in these processes of identification and interpretation is presented, and a list of the pertinent homology criteria is provided.

In humans, the binaural interaction at the brainstem level has been studied for over 15 years. The binaural interaction component (BIC) is obtained by subtracting the summed auditory brainstem response (ABR) in the monaural stimulus mode from the ABR obtained in the binaural stimulus mode. By nature of this subtraction process, the signal-to-noise ratio of the difference waveform is poor, requiring an objective detection criterion to decide whether a significant BIC is present. In this study, the effectiveness of two analysis methods was compared. The first method is the "3 SD' method, which is based on a signal-to-noise evaluation. The second method is a template matching method, in which templates are derived from normal hearing subjects' responses and individual responses are cross-correlated with these templates. The templates were allowed to shift over a range of -0.8 to 0.8 ms in search of the maximum correlation coefficient. Thirty-nine subjects with normal hearing and five patients with a unilateral profound hearing loss participated in the study. ABRs were obtained with rarefaction and condensation clicks at a rate of 15/s and a level of 70 dB nHL. Latencies of the ABR waves I, III and V for all normal hearing subjects and for the normal ear of the patients were within the normal range. The efficiencies of both methods, defined as the number of normal hearing adults with a significant BIC plus the number of patients without a significant BIC divided by the total number of subjects, were determined. The results show that the "3 SD' method is superior to the template matching method: the efficiencies were 95% and 70% respectively, when responses to rarefaction and condensation clicks were taken together. With the "3 SD' method, a significant BIC is demonstrated in almost all normal hearing subjects (97%). However, the "3 SD' method also falsely indicated a significant BIC in one patient. These results suggest that the BIC may have clinical value in studying binaural interaction in humans.

In this chapter the morphogenesis and the general morphology of the CNS of vertebrates will be discussed. As regards morphogenesis, emphasis will be laid on those processes and features that are of direct importance for the interpretation of the parts of the adult brain and spinal cord.

In this paper an outline is presented of the foundations of comparative neuroanatomy. The significance of topology (i.e. the geometry of distortion) for an accurate analysis of the kinds of morphological transformations to which central nervous systems are subjected is emphasized. The major tasks of comparative neuroanatomy are: (1) to sample the variation existing in the central nervous systems on the basis of an analysis of a multitude of carefully selected species; (2) to place the patterns of variation found, wherever possible, in an phylogenetic context; (3) to relate the morphological data and relations determined, to their putative biological (functional, behavioural) significance, and (4) to reflect on the question of which specific factors and processes might have caused the changes through which the brains of organisms have passed, and to develop explanatory scenarios.

The class of bony fishes or Osteichthyes is usually subdivided into two subclasses, the Actinopterygii or ray-finned fishes and the Sarcopterygii or lobe-finned fishes. The subclass last mentioned, the telencephalon of which will be treated in the next chapter, can further be subdivided into the Dipnoi or lungfishes and the Crossopterygii or tassel-finned fishes. The Actinopterygii constitute by far the most abundant group of recent vertebrates. They are usually subdivided into three superorders, the Chondrostei, Holostei, and Teleostei. Interestingly, these three superorders may be considered as representing three subsequent stages or gradations of actinopterygian evolution. The Chondrostei are considered as descendants of the Palaeoniscoidei, a primitive group of paleozoic fishes. During the early and middle Mesozoic times, the Chondrostei were supplanted by the Holostei, which in turn were largely replaced in the last phase of the Mesozoic era and the Cenozoic era by the expanding and now-abundant Teleostei.

Resume Les resultats de l'analyse du developpement embryonnaire du telencephale de Polypterus senegalus, ainsi que d'une courte description du telencephale de l'adulte ont ete compares aux donnees presentes dans la litterature scientifique, concernant le developpement et la structure du telencephale des Chondrosteens (Ch), des Holosteens (H) et des Teleosteens (T). Par l'organogenese et la morphologie de son telencephale, Polypterus presente de nombreux points de ressemblance avec les trois groupes ci-dessus cites. Dans la liste des resultats qui vont etre donnes, nous avons adopte le principe suivant: si le processus de developpement ou la structure dont il est fait mention concerne non seulement Polypterus, mais aussi les autres groupes de Poissons osseux, les initiales de ces groupes (Ch, H, T) seront ajoutees entre parentheses. 1 Comme chez tous les Gnathostomes, la morphogenese du telencephale du Polyptere commence par une inversion legere de ses parois laterales. 2 Par la suite, cette inversion, disparait. Les parois de l'ebauche telencephalique commencent a faire saillie dans la cavite ventriculaire et, correlativement, les taeniae (c'est-a-dire les deux lignes le long desquelles se rattache le toit telencephalique originellement etroit) se deplacent lateralement (H, T). 3 Ulterieurement, les taeniae se deplacent en direction ventrale, et l'apparition de sillons externes bilateraux (sulcus externus) indique les debuts du processus d'eversion (Ch, H, T). 4 Chez les Chondrosteens, les Holosteens et les Teleosteens, c'est l'epaississement des parois telencephalique qui domine pendant reversion; chez Polypterus au contraire, ces parois croissent bien plus suivant leur dimension dorsoventrale qu'en epaisseur. 5 Les bulbes olfactifs apparaissent au debut sous forme d'epaississements des parois telencephaliques. Plus tard, ils prennent la forme d'evaginations separees, possedant en propre leur cavites ventriculaires (Ch, H). 6 Outre reversion et l'evagination reelle bulbaire, une pseudoevagination (Kallen) se produit dans le telencephale de Polypterus. Ce processus conduit a la formation d'un septum ependymaire etendu (Ch, H). 7 Tot au cours du developpement, deux regions, qui sont respectivement l'area dorsalis telencephali ou pallium et l'area ventralis telencephali ou subpallium, peuvent etre distinguees d'apres des differences cytologiques (Ch, H, T). 8 La zone periventriculaire de l'area ventralis telencephali se differencie en un nucleus subpallialis dorsalis et un nucleus subpallialis ventralis (Ch, H, T). D'autres cellules de l'area ventralis migrent vers une position submeningee et forment un noyau subpallialis lateralis (H, T). 9 Une colonne de cellules migrantes dirigee rostroventralement, et provenant de la portion la plus dorsocaudale du manteau subpallie, aboutit a la formation du complexe des noyau entopedonculaires (Ch, H, T). 10 Dans l'area dorsalis telencephali du Polyptere, la couche du manteau embryonnaire persiste chez l'adulte sous forme d'une zone etroite de substance grise periventriculaire. Cette zone ne montre ni aux stades larvaires, ni chez l'adulte, de signe de differenciation en territoires distincts. 11 L'area dorsalis telencephali ou pallium du Polyptere montre un stade d'organisation bien plus simple que celui des Chondrosteens, des Holosteens et des Teleosteens. 12 Une couche cellulaire externe etendue se forme dans la partie rostrale evaginee du telencephale du Polyptere. Comme chez Acipenser, cette couche est en continuite avec la zone glomerulaire et appartient integralement a la formation bulbaire. Abstract In this paper an analysis of the development of the forebrain of Polypterus senegalus, and a short description of the adult telencephalon of that species has been presented. The results of this study have been compared with data obtained from the literature on the development and structure of the forebrain of the Chondrostei (Ch), Holostei (H), and Teleostei (T). It appeared that, with regard to the embryology and morphology of its forebrain, Polypterus shows many points of resemblance to the three groups mentioned. In the subsequent survey of results these similarities have been indicated as follows: if the process or feature mentioned occurs not only in Polypterus, but also in the other bony fish groups, the initials of these groups (Ch, H, T) are added in brackets. 1 As in all Gnathostomes the morphogenesis of the forebrain of Polypterus commences with a slight inversion of its lateral walls. 2 During further development this inversion disappears. The walls of the telencephalic anlage begin to protrude into the ventricular cavity, and concomitantly the taeniae (i.e. the lines of attachment of the initially narrow telencephalic roof plate) move laterally (H, T). 3 Later the taeniae are displaced ventrally, and the appearance of bilateral external grooves (sulci externi) marks the beginning of an eversion (Ch, H, T). 4 In the Chondrostei, Holostei and Teleostei the thickening of the telencephalic walls continues during the eversion, but in Polypterus these walls increase much more in dorsoventral length than in thickness. 5 The bulbi olfactorii develop initially as thickenings of the telencephalic walls. In later stages they assume the configuration of separate evaginations, with ventricular cavities of their own (Ch, H). 6 Apart from eversion and true evagination, an extensive pseudoevagination (Kallen) occurs in the forebrain of Polypterus. This process leads to the formation of an extensive ependymal septum (Ch, H). 7 Early in development two regions, i.e., the area dorsalis telencephali or pallium and the area ventralis telencephali or subpallium can be delimited on account of cytological differences (Ch, H, T). 8 The periventricular zone of the area ventralis telencephali differentiates into a nucleus subpallialis dorsalis and a nucleus subpallialis ventralis (Ch, H, T). Other cells within the area ventralis migrate to a submeningeal position and form a nucleus subpallialis lateralis (H, T). 9 A rostroventrally directed migration of cells, originating from the most dorsocaudal part of the subpallial mantle layer, leads to the formation of a complex of entopeduncular nuclei (Ch, H, T). 10 In the area dorsalis telencephali of Polypterus the embryonic mantle layer persists as a narrow zone of periventricular gray. Neither in the larvae nor in the adult does this zone show signs of a differentiation into separate fields. 11 The area dorsalis telencephali or pallium of Polypterus is much more simply organized than that of the Chondrostei, Holostei and Teleostei. 12 In the rostral, evaginated part of the forebrain of Polypterus an extensive external cell layer is formed. As in Acipenser this layer is coextensive with the glomerular zone and belongs entirely to the bulbar formation.

The nucleus raphe dorsalis of the albino rat has been studied in the following three ways: (1) the cell mass was subjected to a detailed cytoarchitectonic analysis, based upon Nissl-stained material; (2) serotonin--as well as the noradrenaline--immunoreactive neurons present in the area of the nucleus raphe dorsalis were plotted; (3) following large injections of the fluorescent dye propidium iodide into the caudatoputamen complex, the cells in the nucleus raphe dorsalis projecting to this complex were labeled and subsequently stained with an antibody against serotonin. Cytoarchitectonic analysis showed that three cell types are present within the confines of the nucleus raphe dorsalis: small, medium and large. Moreover, differences in concentrations of cell bodies made it possible to subdivide the nucleus raphe dorsalis into four regions. Immunohistochemical analysis showed that the borders of the serotoninergic cell groups B6 and B7 of DAHLSTROM and FUXE do not coincide with those of the nucleus raphe dorsalis. Serotonin-immunoreactive perikarya in the nucleus raphe dorsalis were categorized as medium and large neurons; noradrenaline-immunoreactive neurons in the nucleus raphe dorsalis do all belong to the category--large neurons. With the combined use of immunofluorescence and fluorescent retrograde tracing, it was found that the projection from the nucleus raphe dorsalis to the caudatoputamen complex originates from serotoninergic as well as non-serotoninergic cells, both of which can be categorized as being medium-sized neurons. The data presented in this paper provides a guide for further studies of afferent and efferent connections of the nucleus raphe dorsalis and for electrophysiological experiments on its constituent neurons.

The release of neuronal secretory products by exocytosis in different layers of the median eminence of the rat was investigated ultrastructurally after perfusion with Ringer solution containing tannic acid. Exocytotic images were observed in all layers studied. Neurohaemal release sites were found in the pars externa of the palisade layer, where they occurred not only against the basal lamina of the pericapillary space, but also opposite, adjacent to neuronal and glial elements. In the lateral portion of the pars externa of the palisade layer most release sites were separated from the pericapillary space or the pial surface by ependymal or glial processes. In the pars interna of the palisade layer, and in the reticular, fibre and subependymal layers, release was observed in different types of axonal processes without morphological synaptic specializations. We suggest that products released in the pars externa of the palisade layer are destined to reach the capillaries of the primary portal plexus. Although the non-vascular release sites may serve a similar hormonal function, they may alternatively represent the morphological correlate of axo-axonal contacts or of paracrine, non-synaptic release sites.

The principal auditory leading to the cerebral cortex and therewith to conscious perception passes from the cochlea, via the cochlear nuclei, the inferior colliculus and the medial geniculate body to the contralateral auditory cortex in the temporal lobe. All components of this pathway are cochleotopically organized. The fibre stream leading from the cochlear nuclei to the contralateral inferior colliculus consists of both direct and multisynaptic components. The latter are interrupted one or more times in the superior olivary complex and/or the nuclei of the lateral lemniscus, cell assemblies that lie embedded into the main ascending fibre stream. The auditory cortex receives not only impulses from the contralateral cochlea, but also from the ipsilateral cochlea. The ipsilateral projection reaches the ipsilateral inferior colliculus after a synaptic interruption in the ipsilateral superior olivary complex. Fibres conveying impulses from the contralateral side back to the ipsilateral side are probably also involved. The auditory system of the brain stem is characterized by the presence of several well-developed commissures. Most of these contain, in addition to decussating components, true commissural fibres. The various auditory centres in the brain stem are not only way stations in the ascending auditory pathways, but also serve as relays in descending auditory projections. Most important among the latter is the cortico-cochlear projection which is synaptically interrupted in the inferior colliculus and the periolivary nuclei. The final link in this descending projection is formed by the bundle of Rasmussen, the fibres of which leave the central nervous system and innervate the inner and outer hair cells in the organ of Corti. The pathways for the auditory startle response, the auditory orientation reflex and the stapedius and tensor tympani reflexes are briefly described.

In this paper a survey is presented of the macrostructure and microstructure of the central nervous system of the brachiopterygian fish Erpetoichthys calabaricus, based partly on personal observations and partly on the literature. The spinal cord resembles in its structural organization that of other fish groups. It is, however, remarkable that at lower levels the ventral and dorsal horns are represented by isolated islands of gray without a zona intermedia. In the rhombencephalon the gray matter is arranged in four longitudinal zones or areas which have been termed area ventralis, area intermedioventralis, area intermediodorsalis and area dorsalis. These longitudinal areas coincide largely, but not entirely, with the so-called functional columns of Herrick and Johnston. The most obvious incongruity is that the area intermediodorsalis contains, in addition to the viscerosensory nucleus o the solitary tract, several somatosensory centres. The cerebellum comprises, apart from a pair of large auriculae, a well developed central body. The latter consists of bilateral symmetrical halves which have invaginated into the ventricular cavity. The rostral part of this central body represents the valvula cerebelli, whereas its caudal part represents the corpus cerebelli. Microscopically, the cerebellum contains a molecular layer, a zone of Purkinje cells and a zone of granule cells, but these structures are not arranged in the usual laminated pattern. The medium-sized mesencephalon comprises a ventral tegmentum and a dorsal tectum. The former can be subdivided into a medial zone and a lateral zone. The medial zone may be considered as a direct rostral continuation of the, mainly somatomotor, rhombencephalic area ventralis. The lateral tegmental zone contains, apart from a rather small torus semicircularis, a huge, submeningeally situated, cell mass, which is known as the torus lateralis. The functional significance of this centre is entirely unknown. The tectum shows a distinct laminar pattern which in some respects is more reminiscent to that of anurans than to that of actinopterygian fishes. The fibre systems in the brain stem and spinal cord have not been studied with experimental techniques so far. However, the following pathways could be clearly distinguished in our normal material: (1) several bundles of primary afferent fibres in the rhombencephalic alar plate, (2) a distinct lateral lemniscus, (3) a large fasciculu longitudinalis medialis, comprising vestibulospinal, vestibulomesencephalic and reticulospinal fibres, as well as the giant fibre of Mauthner, (4) a tectobulbar fibre system, (5) a fasciculus retroflexus, (6) a number of fasciculi tegmentales +

The brain stem or truncus cerebri as defined here comprises the derivatives of two of the three primary brain vesicles, viz. the mesencephalon and the rhombencephalon. Both of these brain parts are well developed in the frog. Their importance appears immediately from the fact that they harbor the chief centers of origin and termination of all of the cranial nerves, with the exception of I. In addition, the brain stem of the frog contains a fairly well differentiated reticular formation and a number of sensory and motor relay nuclei with their associated ascending and descending connexions.

The localization and distribution of serotonin (5-HT) has in the rat brain been studied with the indirect immunofluorescence technique of Coons (1958)using a newly developed, specific antibody to 5-HT. This paper contains a detailed description of the distribution of 5-HT in the hypothalamus and hypophyis and a brief report on the localization of 5-HT containing cell bodies. Principally, 5-HT perikarya were present in neuron systems with a distribution similar to that revealed by the mapping of Dahlstrom & Fuxe (1964) with the formaldehyde-induced-fluorescence technique (FIF). However, in addition to the nine areas originally described, several other areas in the mesencephalon and rhombencephalon appeared to contain 5-HT cell bodies. In the hypothalamus no 5-HT positive neuronal perikarya could be observed. However, in the infundibulum and in the median eminence some 5-HT positive tanycytes and mast cells were observed. Serotonergic fibers and terminals are present throughout the hypothalamus. Particularly dense plexus of the fibers and terminals have been observed in the lateral hypothalamic area, nucleus mamillaris medialis, the nucleus perifornicalis, the nucleus suprachiasmaticus and the nucleus ventromedialis hypothalami. All remaining hypothalamic areas demonstrate various densities of 5-HT immunoreactive nerve fibers. In the pituitary 5-HT-like immunoreactivity have been found in the pars nervosa.

A study of the recent neuromorphological, neurophysiological and neuroethological literature, and data from the current research in our own laboratory have led us to a new classification of entities in the mammalian neuraxis. This classification comprises the core and the median and lateral paracores. The core of the neuraxis may be considered as a caudally extended limbic system. It extends throughout the central nervous system and, as its name implies, most of it is situated close to the ventricular cavity. This entity is characterized by the presence of (1) numerous diffuse grisea, (2) enormous amounts of thin, unmyelinated, varicose axons, many of which are arranged in diffuse fibre systems, (3) large numbers of different neuromediators, particularly neuropeptides, and (4) large numbers of neurons which concentrate estrogen and androgen hormones. Ethophysiological studies have shown that the core region contains numerous loci from which on stimulation quite characteristic behavioral patterns, like eating, drinking, fear, attack, reproductive behavior etc., can be elicited. The core region appears to be involved most directly in the organization of behavior and is of paramount importance for the regulation of processes aimed at the survival of the individual (organism) and of the species. The median and lateral paracores represent extensions of the core at the level of the brain stem. The median paracore includes the raphe nuclei, whereas the (bilateral) lateral paracore is constituted by a ventrolaterally extending lamella of tissue. Both paracores contain sets of monoaminergic cells giving rise to networks of fibres that pervade virtually all grisea of the neuraxis, i.e. the serotoninergic neurons in the median paracore and the catecholaminergic cells in the lateral paracore. The lateral paracore contains a series of grisea, including the substantia nigra, the ventral tegmental area, the nucleus reticularis parvocellularis, the tegmental pedunculopontine nucleus and the catecholaminergic cell groups A1, A2, A5, A7 and C1 and C2. It harbours a large bundle of loosely arranged, thin fibres, which forms a direct caudal continuation of the hypothalamic medial forebrain bundle. This lateral paracore bundle contains numerous catecholaminergic and peptidergic fibres. Three typical core centres, viz. the nucleus centralis amygdalae, the bed nucleus of the stria terminalis and the lateral hypothalamic area contribute substantially to this bundle. The lateral paracore contains, just like the core region, a large number of functionally defined centres related to integrated somatomotor and visceromotor responses. It is postulated that non-synaptic interneuron

An electron microscopical morphometric analysis has been carried out at the medullary level of the pyramidal tract of the rat in order to quantify both myelinated and unmyelinated fibers: it was found that unmyelinated fibers outnumber myelinated ones substantially (133,000 ± 18,000 versus 91,000 ± 11,000, respectively). The unmyelinated fibers range from 0.05 to 1 μm in a monomodal distribution (mean 0.16 μm). For myelinated axons also a monomodal distribution was observed (ranges: axon 0.10–4 μm, mean 0.80 μm; myelin sheath 0.25–5 μm, mean 1.19 μm).

The localization and distribution of serotonin (5-HT) has in the rat brain been studied with the indirect immunofluorescence technique of Coons (1958) using a newly developed, specific antibody to 5-HT. This paper contains a detailed description of the distribution of 5-HT in the hypothalamus and hypophyis and a brief report on the localization of 5-HT containing cell bodies. Principally, 5-HT perikarya were present in neuron systems with a distribution similar to that revealed by the mapping of DahlströmFuxe (1964) with the formaldehyde-induced-fluorescence technique (FIF). However, in addition to the nine areas originally described, several other areas in the mesencephalon and rhombencephalon appeared to contain 5-HT cell bodies. In the hypothalamus no 5-HT positive neuronal perikarya could be observed. However, in the infundibulum and in the median eminence some 5-HT positive tanycytes and mast cells were observed. Serotonergic fibers and terminals are present throughout the hypothalamus. Particularly dense plexus of the fibers and terminals have been observed in the lateral hypothalamic area, nucleus mamillaris medialis, the nucleus perifornicalis, the nucleus suprachiasmaticus and the nucleus ventromedialis hypothalami. All remaining hypothalamic areas demonstrate various densities of 5-HT immunoreactive nerve fibers. In the pituitary 5-HT-like immunoreactivity have been found in the pars nervosa.

The present paper is devoted to the extrinsic connections of lobe C3 of the highly differentiated corpus cerebelli of the electric fish Gnathonemus petersi. For this purpose, HRP injections or gels were placed in distinct parts of lobe C3 or its peduncle, in the pretectal region, and in the eye. Moreover, the presence of serotonin and tyrosine-hydroxylase was studied with immunohistochemical methods. The afferent connections of the rostral and caudal part of lobe C3 appear to differ considerably. Although both parts receive comparable projections from two pretectal nuclei (termed nucleus geniculatus and dorsal anterior pretectal nucleus) and the inferior olive, they receive projections from different parts of the nucleus lateralis valvulae, a large cell mass in the midbrain tegmentum, composed of small, tightly packed neurons. The caudal part of lobe C3 receives a projection from the most rostromedial cap of cells of this nucleus, whereas the rostral cap of lobe C3 receives efferents from the neighboring, more caudolateral, zone of cells of the nucleus lateralis valvulae. The caudal part of lobe C3, but not its rostral part, receives an additional projection from a nucleus in the isthmus region, termed nucleus Q. This nucleus sends a collateral projection to the torus longitudinalis. The efferents of both parts of lobe C3 project to slightly different parts of the midbrain tegmentum and the nucleus reticularis superior, and originate at least partly from eurydendroid cells. None of the nuclei and fiber tracts labeled could be shown to contain serotonin or catecholamines. The connections of lobe C3, as revealed by the present study, are compared with those of other parts of the mormyrid cerebellum and with those of the corpus cerebelli of other teleosts, with emphasis on the homology and functional significance of pretectocerebellar connections, the topical order in the cerebellar projections of the nucleus lateralis valvulae, and the relations between the cerebellum and torus longitudinalis. Comparison of the cerebellar connections in different teleostean species suggests that the strong development and the considerable differentiation of the cerebellum of mormyrids are related to at least two types of changes in the extrinsic connections, i.e.: a redistribution or parcelling of connections and the development of connections specific for mormyrids.

A method for measuring the susceptibility of a patient to develop decubitus ulcers is described and initially evaluated. It is based on an indirect, noninvasive measurement of the transient regional blood flow response after a test pressure load which simulates the external stimulus for pressure-sore formation. This method was developed to determine the individual risk of a patient and to study the subfactors which contribute to the susceptibility. This would also offer the possibility of evaluating the effect of preventive treatment aimed at reducing the susceptibility. The method was found to discriminate between preselected elderly patients at risk on the one hand, and non-risk patients and healthy young adults on the other hand. No differences in blood flow responses were found between the non-risk elderly patients and the healthy young adults. This suggests that age per se is not a factor in the formation of pressure sores. In the risk group the recovery time after pressure relief was found to be three times as long as the duration of the pressure exercise. This indicates that the recovery time after pressure exercise may be as important as the period of pressure exercise in deducing the risk of developing decubitus ulcers.

It has been known for a long time (Tiedemann, 1816; Stieda, 1868) that the forebrain of teleosts differs considerably from that of the other vertebrates. It consists of two solid lobes which are separated from each other by a median slit-like ventricle. Lateral ventricles surrounded by nervous tissue, which are found in almost all other vertebrates are lacking, and this is not only the case in the adult stage, but also during development. Thus, the solid condition of the teleostean telencephalic lobes is not due to an obliteration of initially present ventricular cavities, but is rather a primary feature.

R. Nieuwenhuys, H. Bouman, Meer licht over Kartini, met steun van de Van Deventer-Maasstichting uitgegeven bij H.J. Paris te Amsterdam (1954).