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This volume is a collection of essays which attempts to summarize the recent progress in the field of photoreceptor and retinal physiology. Reflecting the way in which research is organized, each author reports on the studies performed with the techniques with which he is most familiar: morpholo gical, chemical or physiological. The first chapters describe the structure of visual cells and the histological architecture of the retina. Next comes a summary of the laws governing photochemical reactions and a report on the biochemistry of photopigments. Four articles cover the optical properties of invertebrate eyes and the electrophysiology and the interactions of their photoreceptors. These are followed by a discussion of the properties of vertebrate eyes, including chapters on optics, on the electrical responses of rods and cones and on the functional organization of the retina. The final chapter provides an extensive review of retinal biochemistry and metabolism. Even though the experimental approach differs, all studies are directed toward the solution of two basic problems: transduction in the photoreceptors and orga nization (often called "information processing") in the retina. The central problem of photoreceptor cells is to determine how light produces a response. We know that illumination evokes electrical changes and we have recently learned a great deal about the features of these changes. The evidence indicates however that elaborate processes must be interposed between the ab sorption of photons by the pigment and the production of electric currents through the membrane. These intermediary cvents remain to be unraveled.
Photoreceptors are nerve end organs or receptors that are sensitive to light. In the retina of the eye, the outer limbs of rods and cones make up the photoreceptor layer. This book presents topical research in the study of the physiology, types and abnormalities of photoreceptors. Topics include the mechanisms for tuning a photoreceptor's spectral sensitivity; foveal microstructure observed by optical coherence tomography; the caudal photoreceptor in the crayfish and quantum catches and photoreceptors.
Ce livre historique peut contenir de nombreuses coquilles et du texte manquant. Les acheteurs peuvent generalement telecharger une copie gratuite scannee du livre original (sans les coquilles) aupres de l'editeur. Non reference. Non illustre. 1880 edition. Extrait: ...Il n'a donc nullement les allures d'un missionnaire ni les visees d'un soldat de la papaute. IL vit terre a terre; il n'a pas d'ideal. Comme organe des passions populaires qu'il enflammerait, il aurait une puissance reelle; mais, s'il voulait maintenant lutter contre les tendances de ses paroissiens, il ne serait pas obei. Le pretre est une puissance electorale quand il peut dire aux fideles: Vous voterez pour un tel, ou je vous refuse l'absolution. Mais, en Italie, il ne songe pas a prendre cette attitude. Il n'ose pas meme interdire la lecture des journaux anticlericaux. Si les liberaux font passer le projet de loi, deja depose, qui remplace les proprietes des cures par une dotation au budget, ils auront supprime le lien qui attache le bas clerge a la societe civile et ils l'auront prepare ainsi a devenir uniquement une milice papale. Ce sera un premier pas. Un second pas sera fait quand, dans les seminaires, les eveques formeront les levites a la lutte politique et surtout quand ils leur auront fait comprendre qu'en s'emparant des electeurs, ils peuvent devenir les maitres de ceux qu'ils craignent aujourd'hui. C'est precisement ce qui se fait maintenant, et les jeunes pretres commencent a entrevoir un ideal d'autorite qu'ils pourront atteindre un jour. Mais, avant qu'ils n'en arrivent la, il faudra qu'ils preparent a leur tour les generations nouvelles a subir leur influence et qu'ils habituent peu a peu les laiques a s'incliner devant leurs...
The vertebrate eye has been, and continues to be, an object of interest and of inquiry for biologists, physicists, chemists, psychologists, and others. Quite apart from its important role in the development of ophthalmology and related medical disciplines, the vertebrate eye is an exemplar of the ingenuity of living systems in adapting to the diverse and changing environments in which vertebrates have evolved. The wonder is not so much that the visual system, like other body systems, has been able to adapt in this way, but rather that these adaptations have taken such a variety of forms. In a previous volume in this series (VII/I) Eakin expressed admiration for the diversity of invertebrate photoreceptors. A comparable situation exists for the vertebrate eye as a whole and one object of this volume is to present to the reader the nature of this diversity. One result of this diversification of ocular structures and properties is that the experimental biologist has available a number of systems for study that are unique or especially favorable for the investigation of particular questions in visual science or neurobiology. This volume includes some examples of progress made by the use of such specially selected vertebrate systems. It is our hope that this comparative approach will continue to reveal new and useful preparations for the examination of important questions.