Our highly seasonal world restricts insect activity to brief portions of the year. This feature necessitates a sophisticated interpretation of seasonal changes and enactment of mechanisms for bringing development to a halt and then reinitiating it when the inimical season is past. The dormant state of diapause serves to bridge the unfavourable seasons, and its timing provides a powerful mechanism for synchronizing insect development. This book explores how seasonal signals are monitored and used by insects to enact specific molecular pathways that generate the diapause phenotype. The broad perspective offered here scales from the ecological to the molecular and thus provides a comprehensive view of this exciting and vibrant research field, offering insights on topics ranging from pest management, evolution, speciation, climate change and disease transmission, to human health, as well as analogies with other forms of invertebrate dormancy and mammalian hibernation.

Animal welfare is attracting increasing interest worldwide, but particularly from those in developed countries, who now have the knowledge and resources to be able to offer the best management systems for their farm animals, as well as potentially being able to offer plentiful resources for companion, zoo and laboratory animals. The increased attention given to farm animal welfare in the West derives largely from the fact that the relentless pursuit of financial reward and efficiency has led to the development of intensive animal production systems, that challenge the conscience of many consumers in those countries. In developing countries human survival is still a daily uncertainty, so that provision for animal welfare has to be balanced against human welfare. Welfare is usually provided for only if it supports the output of the animal, be it food, work, clothing, sport or companionship. In reality, there are resources for all if they are properly husbanded in both developing and developed countries. The inequitable division of the world s riches creates physical and psychological poverty for humans and animals alike in all sectors of the world. Livestock are the world s biggest land user (FAO, 2002) and the population is increasing rapidly to meet the need of an expanding human population. Populations of farm animals managed by humans are therefore increasing worldwide, and there is the tendency to allocate fewer resources to each animal. Increased attention to welfare issues is just as evident for companion, laboratory, wild and zoo animals."

1 Introduction The esophagus is a relatively simple though vital organ. It consists of a two-layered muscular tube whose lumen is lined by squamous strati?ed epithelium. Beyond its role of propelling food from the pharynx to the stomach by a propulsive contraction wave representing the esophageal phase of deglutition (Conklin and Christensen 1994; Jean 2001), it is more and more recognized as a sensory organ from which a variety of respiratory and cardiovascular re?exes can be triggered, thus coop- ating with the larynx in protecting the lower airways from aspiration (Barthelemy et al. 1996; Lang et al. 2002; Lang et al. 2001; Loomis et al. 1997; Medda et al. 2003). In ruminants, there is additional antiperistalsis for regurgitation. During emesis, the esophagus is a merely passive conduit except for some antiperistalsis in its upper part. In the interval between swallows, both oral and aboral ends of the esophagus are tonically closed by the upper and lower esophageal sphincters, UES and LES respectively, while the tubular esophagus is ?accid and partly ?lled with air. Despite this apparent simplicity, neuronal control of esophageal functions is quite complex.

1 Introduction 1. 1 General Remarks The connective and supportive tissues constitute a considerable amount of the biomass in human and animal organisms. Characteristically, the osseous, car- laginous, and ?brous tissues each connect a vital part (cells) with a non-vital part, i. e. , extracellular matrix (ECM). The composition of the ECM constitutes the mechanical qualities of the respective tissue. The functional role of the bone and cartilage tissues is exhaustively discussed in the relevant literature. Whereas bone tissue provides the static and dynamic stability of the system as a whole, cartilage tissue accounts for the power transfer between bones. The articular cartilage insures a fairly friction free mobility of skeletal elements; likewise, cartilage interposed between skeletal elements allows mobility due to its reversible deformability. Under both static and dynamic con- tions, the powers transferred are remarkably large, while the ensuing mechanical force on various tissue zones varies. Tight connective tissue, especially muscle tendons and ligaments, are also part of the skeletal power transfer system. facilitating the transfer of tensile forces. The tendons of the locomotor system serve the purpose of transferring muscular - ergy to those skeletal elements to which they are attached. In this function, they are referred to as tensile tendons ("Zugsehnen"). Inseveral body parts, however, tendons appear in a peculiar mechanical situation: they pass around so-called - pomochlia, i. e. , bony pulleys. Hence, these tendons are referred to as wrap-around tendons ("Gleitsehnen").

Nutrition spans a wide range of mechanisms from acquisition of food to digestion, absorption and retention of energy substrates, water and other nutrients. Nutritional principles have been applied to improving individual health, athletic performance and longevity of humans and of their companion animals, and to maximizing agricultural efficiency by manipulating reproduction or growth of tissues such as muscle, hair or milk in livestock. Comparative nutrition borrows from these tra- tional approaches by applying similar techniques to studies of ecology and physiology of wildlife. Comparative approaches to nutrition integrate several levels of organization because the acquisition and flow of energy and nutrients connect individuals to populations, populations to communities, and communities to ecosystems. Integrative Wildlife Nutrition connects behavioral, morphological and biochemical traits of animals to the life history of species and thus the dynamics of populations. An integrated approach to nutrition provides a practical framework for understanding the interactions between food resources and wildlife popu- tions and for managing the harvest of abundant species and the conservation of threatened populations. This book is for students and professionals in animal physiology and ecology, conservation biology and wildlife management. It is based on our lectures, dem- strations and practical classes taught in the USA, Canada and Australia over the last three decades. Instructors can use Integrative Wildlife Nutrition as a text in wildlife and conservation biology programs, and as a reference source for related courses in wildlife ecology.

This is the first guide to Veterinary Narrative Medicine, a cutting-edge approach in human medicine with multiple applications in veterinary medicine. The text combines the latest research with numerous real-world examples and practical techniques to improve client communication, patient care, and veterinary well-being. Narrative Medicine maintains that a patient should be viewed as an individual rather than an example of a disease process, and that this can be accomplished by using narrative. This book explores methods and theories from leaders in the human Narrative Medicine field while addressing topics unique to veterinary medicine. Readers will gain tools to help navigate difficult conversations and situations in clinical practice, including those involving the end of life. Narrative Medicine in Veterinary Practice also addresses the important issue of veterinary wellness. The ability to view the veterinarian's own stories and those of clients and patients as narratives may help practitioners maintain both emotional and work-place boundaries as well as decrease burnout and compassion fatigue. The book describes basic techniques to promote self-reflection and mindfulness, skills often overlooked in the veterinary profession which can improve resilience and increase the enjoyment of veterinary practice. This is important reading for veterinary practitioners, students, veterinary nurses, technicians, social workers, and all veterinary clinic staff.

The main objective of this book is to present some of the fundamental structural aspects in the design of respiratory organs while debating and speculating on when, how and why these states were founded. The author's main thesis is that the modern gas exchangers are products of protracted processes that have entailed adaptation to specific environments and lifestyles. Only those feasible designs that have proven adequately compentent in meeting demands for molecular oxygen have been preserved. The author's approach has been to look into the limiting functional properties as regards the respiratory capacities of gas exchangers while finding out the specific structural adaptations that have evolved to meet the metabolic needs or to look into form and discern how it limits function.

Mit diesem Nachschlagewerk wird eine systematische Katalogisierung der Losungen angeboten, die dem Designer oder Konstrukteur einen grossen Fundus zur kreativen Umsetzung in der Technik liefert."

This book is a concise summary of the present knowledge about skeletal muscle fibres. The fibre types aare characterized from different points of view. The difficulties and possibilities of classifying muscle fibres in distinct non-overlapping types are shown. A main emphasis is put on metabolic fibre typing by cytophotometry as well as the adaptability of a given fibre type to altered physiological and pathological conditions. Extensive analyses of several rat hindlimb muscles revealed regional differences of fibre properties within the muscles and showed the influence of ageing, myopathy, hypoxia, diabetes and Ginkgo biloba-treatment on the different fibre tyypes.

Ecophysiology attempts to clarify the role and importance of physiological processes in the ecological relations of species in their natural habitats. Including blood collection and the measurement of plasma components and hormone levels, the basic principles and methods relevant to any ecophysiological study are covered in this text. Examples are collected from a wide range of vertebrates living in deserts, cold climates and oceans. The book is an introduction to ecophysiology for advanced students, as well as researchers in ecology, biodiversity and conservation.

Reviews: Methods and Technology in Fish Biology and Fisheries published by Kluwer Academic Publishers is a book series dedicated to the publication of information on advanced, forward-looking methodologies, technologies, or perspectives in fish and is especially dedicated to relevant topics addressing global, fisheries. This series international concern in fish and fisheries. Humans continue to challenge our environments with new technologies and technological applications. The dynamic creativity of our own species often tends to place the greatest burden on our supporting ecosystems. This is especially true for aquatic networks of creeks, lakes, rivers and ocean environments. We also frequently use our conceptual powers to balance conflicting requirements and demands on nature and continue to develop new approaches and tools to provide sustainable resources as well as conserve what we hold most dear on local and global scales. This book series will provide a window into the developing dynamic among humans, aquatic ecosystems (both freshwater and marine), and the organisms that inhabit aquatic environments. There are many reasons to doubt the increasing social and economic value technology has gained over the last two centuries. Science and technology represent stages in human development. I agree with Ernst Mayer when he said in Toward a New Philosophy of Biology (1988) that "endeavors to solve all scientific problems by pure logic and refined measurements are unproductive, if not totally irrelevant.

The aim of this study was to investigate the development and diffferentiation of the adrenal glands in the grass snake during early stages of ontogenesis. After light microscopy and ultrastructural investigation, six developmental phases were distinguished in the grass snake adrenal glands. Similar developmental phases were described in pig embryos but they slightly differ from those presented above. In reptile and mammal embryos a similar direction of changes is observed in primaordia of both tissues forming adrenal glands.

Biophysics and Psychophysics of Photoreceptors.- Visual Pigments and Colour Vision in Primates.- The Cost of Trichromaticity for Spatial Vision.- Variability in Cone Populations and Implications.- Discussion: Biophysics and Psychophysics of Photoreceptor.- Transition from Photopic to Scotopic Light Assessments and Possible Underlying Processes.- Dual Rod Pathways.- Wavelength-Discrimination with Only Rods and Blue Cones.- Density of Bipolar Cells in the Macaque Monkey Retina.- Discussion: Rod Vision.- Parvocellular and Magnocellular Pathways and Psychophysics.- Which Cells Code for Color?.- Receptive Field Structure of P and M Cells in the Monkey Retina.- On the Relation between Cellular Sensitivity and Psychophysical Detection.- P and M Pathway Specialization in the Macaque.- The Color-Opponent and Broad-band Channels of the Primate Visual System.- Discussion: P- and M-Pathways I.- Temporal Characteristics of Colour Vision: VEP and Psychophysical Measurements.- The Contribution of Colour to Motion.- Functional Classification of Parallel Pathways.- The Responses of Macaque Retinal Ganglion Cells to Complex Temporal Waveforms.- Remote Surrounds and the Sensitivity of Primate P-Cells.- On Neurophysiological Correlates of Simultaneous Colour and Brightness Contrast as Demonstrated in P-LGN-Cells of the Macaque.- Development of Infant Contrast Sensitivity and Acuity for Coloured Patterns.- Psychophysical Evidence of two Gradients of Neural Sampling in Peripheral Vision.- Discussion: P- and M-Pathways II.- Visual Evoked Potentials.- On the Nature of Visual Evoked Potentials, Unit Responses and Psychophysics.- Localization of the Electromagnetic Sources of the Pattern Onset Response in Man.- Discussion: Evoked Potentials.- Cortical Processing and Psychophysical Measurement.- Probing the Primate Visual Cortex: Pathways and Perspectives.- Lateral Interactions in Visual Cortex.- The Perceptual Significance of Cortical Organization.- Orientation and Spatial Frequency Selectivity: Properties and Modular Organization.- Orientation and Color Columns in Monkey Striate Cortex.- Discussion: Cortical Processing.- Psychophysical Studies and Post-Receptoral Processes.- Visual Photometry: Relating Psychophysics to some Aspects of Neurophysiology.- Sensory and Perceptual Processes in Seeing Brightness and Lightness.- Assimilation Versus Contrast.- On Achromatic Colors.- Color Opponency from Eye to Brain.- Chromatic Mechanisms beyond Linear Opponency.- Discussion: Psychophysics and Post-Receptoral Processes I.- Adaptation Mechanisms in Color and Brightness.- Testing the Contrast Explanation of Color Constancy.- Adaptation and Color Discrimination.- Studies on Colour Constancy in Man Using a "Checkerboard - Mondrian".- Discussion: Post-Receptoral Processes II.- Models, Neural Processes and Psychophysics.- Origin of Perceptually Measured Phase Shifts in the Visual System.- Psychophysical Correlates of Parvo Channel Function.- On the Physiological Basis of Higher Colour Metrics.- Neural Decoding.- Effects of Phase Shifts between Cone Inputs on Responses of Chromatically Opponent Cells.- Different Neural Codes for Spatial Frequency and Contrast.- Displacement Estimation, Stereo Matching and 'Object' Recognition: A Computer Simulation Approach Working with Real World Imagery.- Scaling and Thresholds of Color and Light Described by an Opponent Model of Color Vision Based on Psychophysical Data.- Discussion: Models and Neural Nets.- General Discussion.- Participants.

In most terrestrial and aquatic habitats, the vast majority of animals transmitting and receiving communicative signals are arthropods. This book presents the story of how this important group of animals use pheromones, sound, vibration, and light for sexual and social communication. Because of their small to minute body size most arthropods have problems sending and receiving acoustic and optical information, each of which have their own severe constraints. Because of these restraints they have developed chemical signaling which is not similarly limited by scale. Presenting the latest theoretical and experimental findings from studies of signaling, it suggests that close parallels between arthropods and vertebrates reflect a very limited number of solutions to problems in behavior that are available within the confines of physical laws.

The rapid development of molecular biology and genetics has led to renewed interest in embryology, comparative embryology, and studies of the relations between ontogeny and phylogeny. In fact, genes have been identified which are involved in the formation of shapes and structures, and it is becoming apparent that their primary morphological expressions are conspicuously similar in different species. The primarily identical shapes do not become diversified until advanced individualization of embryos, and it is here that it is possible to employ the knowledge of comparative embryology, the branch of science engaged in the study of the development and differentiation of tridimensional structures in different animal groups. However, comparative embryology has been neglected during the past decades, as its development has appeared to have been completed. In our opinion, the decreased interest in comparative embryology has been caused by the fact that often the time factor was not or could not be respected. In fact, in the case of embryos of wild animals even their ontogenetic age and sometimes the duration of intrauterine development are unknown.

Sex differences are observed in various physiological, behavioral, and psychic functions, including reproductive behavior, aggres sion, emotions, and cognition. Such differences are expressed even in early childhood with preferences to definite activities. It has been generally accepted that differences between genders are formed under the influence of biological as well as environmental factors. The existence of sex differences in functions of the central nervous system has suggested that there are also morphological sex differences. In recent years several reports on sexual dimorphism in the brain of vertebrates have been published. However, the mecha nisms of sexual differentiation of the central nervous system remain unclear in most cases. It is often difficult to correlate morphological sex differences to differences in definite function or behavior. We set out to explore the sexual dimorphism of the limbic system and especially the bed nucleus of the stria terminalis and the amygdala, which are considered generally to be occupied with the control of reproductive behavior and autonomic and compli cated psychic functions. Several reports on sexual dimorphism of these structures have been published. Some of them have been directed to the total neuronal number and the volume of the nuclei, while others have concentrated on definite subpopula tions of neurons. In many cases the mechanisms of sexual differ entiation were tested, but sometimes they could not be estab lished."

Neurology for the Small Animal Practitioner is a practical presentation of common neurological conditions seen in a small animal practice. The book includes clear guidelines for effective diagnosis and treatment protocols for common neurologic conditions in dogs and cats. Important neurologic pathways and diagnostic procedures are illustrated by original, anatomic drawings and step-by-step procedural figures. Tables and algorithms are used to focus the reader on critical steps in patient evaluation and differential diagnosis. Color illustrations facilitate localization of lesions and patient assessment. The consistent layout, 157 illustrations (102 color), 25 diagnostic images, and 57 tables facilitate the rapid acquisition of information. Published by Teton New Media in the USA and distributed by Manson Publishing outside of North America.

Contents:
Part 1. Insulin Signaling 1. Overview: Tyrosine Kinase Signaling in Insulin Action Martin G, Meyers, Jr. 2. Defects in Early Insulin Signaling in Skeletal Muscle M. Dodon Michel and C. Ronald Kahn 3. Defects in Intermediate Insulin Signaling in Skeletal Muscle: (PI) 3-kinase and Glucose Transport Francesco Giorgino Part 2. Glucose Transport 4. Glucose Transport in Muscle John O. Hollozsy and Lorrine A. Nolte 5. The GLUT4 Compartments of Skeletal Muscle Toolsie Ramlal, Peter Tong, Tony Lam, Romel Somwar, Maureen Charron and Amira Klip Part 3. Substrate Utilization 6. Adverse Metabolic Consequences of Hyperglycemia ('Glucose Toxicity'): Implications for the Pathogenesis of Diabetes Mellitus Donald A. McClain 7. Cellular Mediators of Glucose-Induced Autoregulation of Hexose Transport Evgenia Alpert, Hanan Totrie and Shlomo Sasson 8. Physiological Adaptations in Glucose Utilization of Skeletal Muscle Julian M.R. Mathoo and Mladen Vranic 9. Fatty Acids and Muscle Insulin Resistance Edward W. Kraegen, Gregory J. Cooney, Jiming Ye, Alison L. Thompson and Stuart M. Furler 10. Role of AMP Kinase and Malonyl CoA in Exercise-stimulated Skeletal Muscle Metabolism and Insulin Action David J. Dean and Neil B. Ruderman Part 4. Transgenic and Genetic Models 11. The Use of Mouse Transgenic and Homologous Recombination Technologies to Analyze the Physiologic Basis of Glucose Homeostasis Silvia Mora and Jeffrey E. Pessin 12. Transgenic Approaches to Insulin Signaling Yasuo Terauchi and Takashi Kadowaki 13. Transgenic Models to Study Glucose Transport and Metabolism in Skeletal Muscle Armelle Leturque and Anna-Maria Lombardi Part 5. Diabetic Animals 14. Insulin Resistance in Skeletal Muscle: a Role for Impaired Insulin Activation of Glycogen Synthase Heidi K. Ortmeyer 15. Muscle GLUT4 Traffic and Insulin Resistant States Antonio Zorzano, Eva Tomas, Marta Camps, Anna Guma and Manuel Palacin 16. Glucose Transport in Heart: Special Emphasis on Insulin Resistance and NIDM Jurgen Eckel 17. Cellular Redox State and Insulin Sensitivity: Potential Role of Lipoic Acid Assaf Rudich and Nava Bashan Part 6. Exercise and Aging 18. Exercise Training and Muscle Insulin Resistance: Cellular Adaptations John L. Ivy 19. Effects of Physical Exercise on the Decreased Insulin Action Caused by Aging Yuzo Sato 20. Effects of Aging on Glucose Homeostasis: Cellular Approaches Gregory D. Cartee Part 7. Application to Humans 21. Insulin Resistance: Whole Body Mechanisms in Humans Hannele Yki-Jarvinen 22. Cellular Mechanisms Dana Galuska and Anna Krook

3* Doody's Star Rating (R) CHOICE Magazine 'Recommended' (May 2020) As of 2018, pet obesity in the US affects an estimated 55.8 percent of dogs and 59.5 percent of cats, resulting in secondary conditions such as arthritis, diabetes mellitus, kidney disease, and certain forms of cancer. A complete and balanced diet accompanied by regular exercise is fundamental to optimize health and longevity in companion animals, meaning overweight pets have reduced quality of life and shorter life expectancy. Seeking to address this major modern-day problem, this book provides a comprehensive review of obesity in small animal medicine. Reviews epidemiology and how animal- and human-specific factors contribute to excess weight gain. Discusses the metabolic effects and inflammatory mediators associated with adiposity. Looks at various disease states and how they relate or develop as a result of obesity. Reviews different modalities to determine body composition to diagnose obesity. Offers a clinical approach to managing obesity with diet including discussion on the nutrients of concern for therapeutic weight loss diets. Veterinarians seeking to provide weight management services in practice will find clinically-applicable information from expert authors from both academic and practice backgrounds. Chapters cover topics ranging from epidemiology and pathophysiology of obesity to evaluation of body composition, and nutritional and behavioral management. The book also explores the role of exercise in managing obesity and looks at the management of co-morbidities. Finally, the authors present a range of case studies to demonstrate these topics in real-life practice.

Preparatory work for this monograph started in 1988 and 1989. The motive was provided by certain incongruities in the illustra- tion of descensus testis for the chapter "Entwicklung der Genital- organe" in the book Humanembryologie. The evoked discussion was reason enough for our own re- search on the phenomenon and uncertainties of testicular des- cent in human. The basis ofthese investigations was the collection of human embryos founded by Prof. Hinrichsen in 1970 at the Department of Anatomy and Embryology, Ruhr-University Bo- chum. The preparation of the material used in this paper has been done with the help of many staff members of our department to whom we feel obliged. We are especially indebted to Prof. Hin- richsen who prepared the foetuses and took the first steps of this project. We wish also to acknowledge Dr. Heinz Jiirgen Jacob for careful fixation and microdissection of specimens intended for scanning electron microscopy. Weare also grateful to Mrs. Vera Mannheim for her involvement and her sensitivity in making scanning electron micrographs, and Mrs. Antje Jaeger for provid- ing an expert and skilful photographic technique especially in the setting up of micrographs. Our thanks are also due to Mrs. Marion Kohn for skilful technical assistance and to all those technical assistants who worked in our department during the past 25 years and who were engaged in providing the serial sec- tions. The English text has been thoroughly revised by Prof. Dr.

Morphogeny of the nasal skull was investigated in 92 embryos of 13 species of Cetacea. Compared to the original nasal capsule of land mammals, the nasal structures of Cetacea show many weighty transformations. As a result, the nostrils are translocated from the tip of the snout to the vertex of the head. Several structures of the embryonic nasal skull remain preserved even in adult cetaceans. The translocation of the nostrils to the highest point of the surfacing body is among the most perfect adaptations of cetaceans to the aquatic life habits. The morphogeny of the nasal skull suggests that all cetaceans are of common origin and form a single monophyletic order. The hitherto usual division of this order into two suborders, Mysticeti and Odontoceti, appears to be unsubstantiated. Rather, at least three closely related superfamilies should be distinguished within the order Cetacea, viz., Balaenopteroidea, Physeteroidea, and Delphinoidea. The results are in a

In this treatise, current knowledge on the neurogenesis, axonal outgrowth, synaptogenesis, and regenerative capacity of descending supraspinal pathways in tetrapods is discussed. Although emphasis is on the clawed toad, Xenopus laevis, chicken embryos, opossums and rodent data, also the data available for primates including man are presented. It will be shown that 1) the outgrowth of descending supraspinal pathways is the result of a coordinated program; 2) the pattern of early descending axonal tracts is similar in all vertebrate groups; 3) the formation of descending supraspinal pathways occurs according to a developmental sequence; 4) the earliest descending supraspinal fibers arrive in a rather immature spinal cord, and 5) the regenerative capacity of descending supraspinal pathways depends on the developmental stage the particular pathways arise.

Only five years ago, nobody in his right mind would have consid ered publishing a book on reeler as a model for brain develop ment. Although this interesting mutation has been with us for half a century, it is fair to say that, in spite of a wave of enthusiasm in the late sixties and early seventies, generated primarily by Sidman, Caviness and colleagues, studies of reeler mice fell pro gressively out of fashion during the next two decades. All that changed almost overnight when the cloning of the reeler gene, dubbed reelin, was reported in Tom Curran's laboratory in 1995. The fact that the same gene was identified at the same time independently by two other groups using positional cloning sug gested strongly that reelin was the right candidate. Although the key experiments of transgenic rescue have not been made (and perhaps will never be), the equation "reeler is reelin" has been established beyond reasonable doubt, as alterations of the reelin gene and/or its expression have been found in at least five alleles of reeler and in the mutation Shaking Rat Kawasaki (SRK), an ortholog of reeler."

Due to their pronounced intraspecific variability and to difficulties in defining their evolutionary trends in mammalian phylogenies, peripheral blood vessels have been neglected in comparative studies. Supported by the Sonderforschungsbereich 89 (Car- diology) of the Deutsche Forschungsgemeinschaft, we have reconstructed the ontoge- of the blood vessels of the tree shrew, Tupaia belangeri, on the netic morphogenesis basis of a series of developmental stages. The arteries of the lower extremity are described and discussed here. Besides describing the morphogenesis of the arteries in Tupaia, it is the aim of this study to explain the variability of the arteries of the pelvic extremity among mammals, and especially among primates including man, on the basis of a common developmen- tal pattern. This can be shown in the following example. In the popliteal region of most adult mammals the arteria poplitea profunda is situated under the musculus popliteus. In the adult Tupaia, as well as in primates, this artery is missing but, superficial to the musculus popliteus, an arteria poplitea super- ficialis exists. It seems difficult to explain such a case of "discontinuous evolution," because it is hard to imagine the position of the artery should have shifted through the muscle. The present investigation and the literature show that early in the embryonic development of a primate, man, and of Tupaia, both the arteria poplitea profunda and the arteria poplitea superficialis are present.

During pubertal development of the testes, germ cells pass initially through the complete succession of spermatogenic differentiation. Using the golden hamster as a model, this volume presents a comprehensive analysis of that establishing period of mammalian spermatogenesis. Detailed morphological and cell kinetic data of the pubertal seminiferous epithelium reveal a level of cellular organization and synchronization coming near to the adult situation. Characteristic, temporarily occurring perturbations of spermatogenic progression are related to specific delays of Sertoli or Leydig cell maturation, respectively. These results emphasize and specify the close structural and functional interdependence of germ and somatic cell development.