This second edition is more extensive and detailed than the previous one - now a reference of two decades standing. New technical methods have increased our understanding of many tumours, and the earlier group of monomorphic adenomas has been separated for easier identification, while clearly defined tumours - even if uncommon - have their own category. With reference to their differences in prognosis and treatment, the various types of carcinomas are now listed separately, and new entities have been adopted. The inclusion of the TNM classification of salivary gland tumours together with the more detailed description of the tumour-like lesions will contribute to an even better understanding.

Experimental results reached by the authors as well as various hypotheses previously advanced by other research workers are examined in this volume. The authors' study of the course of bloodstreams in the ventricular outflow tract and in the 6th and 4th branchial arterial arches points to 13 hemodynamic patterns and 13 changes in the direction of the endocardial septal ridges. They describe the hemodynamic processes of development of several well-known malformations of the great arteries and of other vascular anomalies that have not been identified morphologically. The authors conclude that it is possible in this way to correctly explain the cardiovascular malformations that have been obtained experimentally.

This classification is based primarily on the microscopic characteris- tics of tumours. It is therefore concemed with the identification of cell types and histological pattems as seen by conventional light mi- croscopy. In general, time-honoured terms have been retained. Syn- onyms are listed only if they have been widely used, or if they are considered to be important for understanding the disease process. In such cases the preferred term is given first, followed by the synonym in parentheses. The individuality of the tumour manifests itself principally in its histological appearance and the extent of spread at the time of diag- nosis. This volume is concemed only with the histological classifica- tion of tumours. Anatomieal extent or staging is covered in the TNM 1 Classification. The histological classification of a tumour depends on two main parameters, typing and grading, and a number of additional parame- ters which may apply to selected examples.

To give an update in the field of haemostasis scientists and clinicians fromoverseas and European countries met to dis- cuss the new trends in pathophysiology and clinical impli- cations. This book is devoted to the interactions of endo- thelial functions, tissue factors, coagulation inhibitors and haemostasis as well as detection and prophylaxis of thromboembolism. Data are presented of significant new re- search work on molecular and clinical approaches to diseases in haemostasis.

This book provides a comprehensive survey of the structure and fiber connections of the human midbrain, specifically of the substantia nigra and ventral tegmental area. The cellular and chemical architecture of these structures is analyzed and the structures' fiber connections are discussed. The role that they play in degenerative diseases of the nervous system, such as Alzheimer's and Parkinson's diseases, is evaluated. Some functional and pathophysiological considerations are included.

Concise yet comprehensive, Cytology: Diagnostic Principles and Clinical Correlates is a practical guide to the diagnostic interpretation of virtually any cytological specimen you may encounter. This highly useful bench manual covers all organ systems and situations in which cytology is used, including gynecologic, non-gynecologic, and FNA samples, with an in-depth differential diagnosis discussion for all major entities. As with previous editions, the revised 5th Edition focuses on practical issues in diagnosis and the use of cytology in clinical care, making it ideal for both trainee and practicing pathologists. Uses easy-to-read, bulleted text to provide a quick review of key differential diagnoses, indications and methods, cytomorphologic features, clinical pearls, and tissue acquisition protocols for specific entities. Includes coverage of patient management in discussions of pertinent clinical features and emphasizes clinical correlation throughout. Examines the role of immunohistochemistry, flow cytometry, and molecular biology in resolving difficulties in interpretation and diagnosis. Features more than 550 full-color illustrations that provide a real-life perspective of a full range of cytologic findings. Discusses hot topics such as new diagnostic biomarkers and their utility in differential diagnosis, the latest Bethesda System classifications/terminology, new techniques, and new adjunct tests. Provides an in-depth analysis of common diagnostic pitfalls to assist with daily sign-out and reporting. Includes a video on how to perform fine needle aspiration biopsy, from the patient interview and precautions to demonstration of techniques. Enhanced eBook version included with purchase. Your enhanced eBook allows you to access all of the text, figures, and references from the book on a variety of devices.

This text describes a system of reporting breast fine needle aspiration biopsy that uses five clearly defined categories, each described by a specific term and each with a specific risk of malignancy. The five categories are insufficient/inadequate, benign, atypical, suspicious of malignancy and malignant. Each category has a risk of malignancy and is linked to management recommendations, which include several options because it is recognized that diagnostic infrastructure, such as the availability of core needle biopsy and ultrasound guidance, vary between developed and low and middle income countries. This text includes key diagnostic cytological criteria for each of the many lesions and tumors found in the breast. The cytopathology of specific lesions is illustrated with high quality photomicrographs with clear figure descriptions. Chapters also discuss current and potential future ancillary tests, liquid based cytology, nipple cytology and management. An additional chapter provides an overview of an approach to the diagnosis of direct smears of breast fine needle aspiration biopsies. The International Academy of Cytology Yokohama System for Reporting Breast Fine Needle Aspiration Biopsy Cytopathology provides a clear logical approach to the diagnosis and categorization of breast lesions by FNAB cytology, and aims to facilitate communication with breast clinicians, further research into breast cytopathology and related molecular pathology, and improve patient care.

This book provides a highly accessible introduction to anatomy and physiology. Written for students studying the subject for the first time, it covers the human body from the atomic and cellular levels through to all the major systems and includes chapters on blood, immunity and homeostasis. Logically presented, the chapters build on each other and are designed to develop the reader's knowledge and understanding of the human body. By the end of each chapter, the reader will understand and be able to explain how the structures and systems described are organised and contribute to the maintenance of health. Describing how illness and disease undermine the body's ability to maintain homeostasis, this text helps readers to predict and account for the consequences when this occurs. Complete with self-test questions, full colour illustrations and a comprehensive glossary, this book is an essential read for all nursing and healthcare students in both further and higher education.

This book is directed at advanced undergraduate and postgraduate students-and their teachers-who are involved in those areas of cell biology which require a basic knowledge of cytoskeletal structure, parti cularly with respect to cell motility. It contains a core of basic information on the cytoskeleton and focuses especially on its functional aspects, from the swimming of spermatozoa to the crawling of cultured cells across their culture dish; from the transport of vesicles and organelles along nerve axons, to the orderly segregation of chromosomes at mitosis. Cytoskeleton research spans a wide range of scientific disciplines. It is as important for students or research workers investigating, for example, the deposition of the higher plant cell wall to have easy access to a core of basic information regarding microtubules as it is for someone interested in endocytosis and the fate of cell surface receptors. The authors are involved in the teaching of the cytoskeleton and cell motility at all levels of undergraduate study at University College London, but each has a research interest in different aspects of the subject: TMP in amoeboid locomotion, CAK in gliding motility and JSH in cilia, flagella and mitosis.

Two research centers joined to study the development of numerous malformations of the vertebral column in 30 mutants of the laboratory mouse: the Department of Anatomy of the University of Zurich, that has long been a center of research in vertebral anatomy and pathology, and the Jackson Laboratory in Bar Harbor, Maine, the largest center of research in mouse genetics. This volume describes the normal and abnormal morphogenesis of vertebrae and summarizes the data presently available in order to give better insight into the developmental mechanics of the vertebral column.

Seeking Symmetry: Finding patterns in human health offers a guide through the overwhelming mass of data generated by contemporary science. Starved for the knowledge that would best help us stay healthy, we are simultaneously glutted with an overload of information about the human body. Amidst ubiquitous talk that patient-centred care and lifestyle changes are the keys to personal health, self-neglect and medical overtreatment nevertheless prevail. The body is rich with symmetries, many of them unknown to us who live in these bodies. Symmetry-seeking reveals certain patterns for understanding the information we have about the body, patterns whose roots lie in embryonic development and in evolution. The book's exploration will guide readers through the parts of their own bodies and introduce tangible, visible examples of symmetry, not only right and left but up and down, male and female, inside and out, as well as symmetries between humans and other species.It presents the symmetries of the body's internal structures that, despite their complexity, are nevertheless simple to understand when viewed with an eye for pattern.Through both words and images, this book will illustrate the most foundational of the principles, structures, and processes that decide how bodies function.A core purpose of the book is to present this knowledge through a lens that makes the information meaningful, by modelling the habit of symmetry-seeking.

This volume provides an interdisciplinary approach to this central research topic. Firstly, the hippocampus is presented generally as a model for experiments on neurotransmission in the central nervous system; secondly, special features of synaptic organisation and synaptic transmission in this area of the brain are introduced. Of particular note is the wide-ranging methodological approach which includes light and electron microscopy, immunocytochemistry, Golgi/EM techniques, intracellular differentiation and intracellular colorings, histochemistry of transmitter enzymes and receptoraudiography. The reader thereby gains insight into the broad scope of methodological possibilities for the examination of such a complex problem as neurotransmission in the hippocampus.

Nearly 10 years have elapsed since I finished writing the first edition of Intro duction to Molecular Embryology. During this period, molecular embryology has made great strides forward, but without undergoing a major revolution; there fore, the general philosophy and outline of the book have remained almost un changed. However, all the chapters had to be almost completely rewritten in or der to introduce new facts and to eliminate findings which have lost interest or have been disproved. There was a major gap in the first edition of this book: very little was said about mammalian eggs despite their obvious interest for mankind. Research on mammalian eggs and embryos is so active today that this important topic deserves a full chapter in a book concerned with molecular embryology. Therefore, I am very thankful to my colleague Dr. Henri Alexandre, who has written a chapter on mammalian embryology (Chap. 9) and has prepared all the illustrations for this book."

6 Acknowledgments 87 7 References 88 Subject Index 95 VIII Abbreviations A cerebral aqueduct anterior deep dorsal nucleus, CGM AD AP anterior pretectal nucleus AR auditory radiation ASD anterior superficial dorsal nucleus, CGM BA brachium, accessory (medial) nucleus, IC BIC brachium of inferior colliculus BSC brachium of superior colliculus cerebellum CB CC caudal cortex, IC CF cuneate fasciculus CG central gray CGL lateral geniculate body medial geniculate body CGM commissure of inferior colliculus CIC CIN central intralaminar nucleus CL lateral part of commissural nucleus, IC CM central medial nucleus CN central nucleus, IC CORD spinal cord CP cerebral peduncle CSC commissure, SC CUN cuneiform area, IC D dorsal nucleus, CGM DA anterior dorsal nucleus, CGM DC dorsal cortex, IC DD deep dorsal nucleus, CGM DI dorsal intercollicular area DM dorsomedial nucleus, IC DMCP decussation of superior cerebellar peduncle DS superficial dorsal nucleus, CGM EYE enucleation FX fornix GN gracile nucleus HIT habenulo-interpeduncular tract inferior colliculus IC III oculomotor nerve IN interpeduncular nucleus L posterior limitans nucleus LC laterocaudal nucleus, IC LI lateral intercollicular area LL lateral lemniscus lateral mesencephalic nucleus LMN LN lateral nucleus, IC LP lateral posterior nucleus LPc caudal part of lateral posterior nucleus LV pars lateralis, ventral nucleus, CGM M medial division, CGM MB mammillary bodies middle cerebellar peduncle MCP MES V mesencephalic nucleus of trigeminal tract MI medial intercollicular area ML medial lemniscus MLF medial longitudinal fasciculus MT mammillothalamic tract MZ marginal zone, CGM OC oculomotor nuclei occipital cortex lesion OCC OT optic tract

Insectivores are considered to be primitive among the Eutheria and are therefore of particular interest (Romer 1966). In spite of this basal position of the group there are only few papers dealing with the structure of the female reproductive tract in insectivores. Erinaceus has been studied by Deanesly (1934), Talpa by Matthews (1935), some Centetinae from Madagascar by Feremutsch (1948) and Feremutsch and Strauss (1949), and Tenrec by Nicoll and Racey (1985). Among the Soricidae (shrews), Sorex (Brambe1l1935), Blarina (Pearson 1944), Neomys (price 1953), Suncus (Dryden 1969), and Crocidura (Besan~on 1984) have been investigated, but only at the light microscopical level. The first electron micro- scopical studies in this field dealt with oogenesis in Crocidura, Neomys and Sorex (Kress 1984a, b) and with the uterus of the hedgehog (Lescoat et al. 1984, 1985). The aim of this publication is to describe the female genital tract of the shrew Crocidura. The following elements were investigated: bursa ovarica, epoo- phoron, paroophoron, tuba uterina, and the uterus together with the cervix and vagina (Fig. 1). Wherever possible, morphological features are correlated with the functional changes during the annual cycle. The information serves on the one hand as a guideline for interpreting findings in ancestors, such as the monotremes and marsupials, and on the other, together, with data gained from more highly evolved mammals including man, to establish similarities as well as differences. The family Soricidae includes two subfamilies, the Soricinae (or red-toothed shrews) and the Crocidurinae (white-toothed shrews).

In birds, the beak is the most important organ for manipulative actions: its manipulative capabilities vary as much as those of the forepaws and snouts of mammals. For the peripheral parts and at brainstem levels, the sensorimotor circuit of the avian oral region is roughly similar to the mammalian, but is strikingly different at higher levels of the central nervous system (CNS) (Ariens- Kappers et al. 1936). Our field of interest is the organization of the telencephalic areas involved in the manipulative actions of the bill. The goose was chosen as a subject because of the extensive development of the tactile system of the oral region. The mechanoreceptors in the lower and upper beak are innervated by the trigeminal nerve (Cords 1904; Berkhoudt 1980), while the tongue is innervated by branches of the glossopharyngeal and hypoglossal nerves (Cords 1904). In the ganglion semilunare, the perikarya of the fibers of the trigeminal nerve are separated into a distinct ophthalmic population, and two mutually overlap- ping maxillary and mandibulary populations (Dubbeldam and Veenman 1978; Noden 1980). In duck and cockatoo both the glossopharyngeal nerve and trige- minal nerve relay in the metencephalic principal sensory nucleus of the trige- minal nerve (PrV) (Dubbeldam et al. 1979; Dubbeldam 1980; Wild 1981). In PrY the three trigeminal branches are represented in an overlapping dorsoventral sequence (Zeigler and Witkovsky 1968; Dubbeldam and Karten 1978).

At the end of the nineteenth century, controversy arose as to precisely when the first glial cells originate during development of the central nervous system, and to date, the issue has not been satisfactorily resolved. His (1889, 1890) noted that, even in the earliest developmental stages of the germinallayer, there appeared to be two distinct cell types. The cells which he called Spongioblasten were thought to be glial precursors from which all mature glial cells derive; Keimzellen, in contrast, were regarded as forming 1 neurons. His was working on the assumption that the very first preneurons migrate into a preexisting framework of glial eelIs. In contrast to this view, Schaper (1897) regarded both Keimzellen and Spongioblasten as belonging to a common population of proliferating and pluripotent stem cells which begin differentiation into glial and neuronal cells at late developmental stages. It is this latter view which is the basis of the most recent studies on the subject (e. g. , Caley and Maxwell1968a, 1968b; DeVitry et al. 1980). The concept of one common stem cell seemed to be supported both by experiments using 3H-thymidine autoradiography (Fujita 1963, 1965b, 1966; Sauer and Walker 1959; Sidman et al. 1959) and by ultrastructural studies (Fu- jita 1966; Hinds and Ruffet 1971; Wechseler and Meller 1967) indicating that structural differences, which His presumably used to define his two cell types, could be related to different stages of the mitotic cycle.

Though more than 300 years have elapsed since the first description of the peculiar course of the spinal accessory (XI) nerve by Willis (1664), the crucial problems concerning what is known as accessory field of musculature and its innervation are still unsolved and a matter of controversy. Like the bulbar XI, the spinal XI nerve is commonly regarded as originally a branch of the vagus and, therefore, as a cranial nerve (Fiirbringer 1897; Gegenbaur 1898; Lubosch 1899). However, whether this nerve is of special visceral or somatic derivation is still debated. The conventional distinction between these function ally separate categories of cranial nerves is based largely on two criteria, namely, the position of the cranial nerve nucleus and the embryological derivation of the muscles innervated by this nerve. Unfortunately, little is known about the development of this accessory field of musculature, and the evidence concern ing the position of the spinal XI nucleus is contradictory. In fact, although the spinal XI nerve is usually regarded as a purely efferent nerve belong ing to the special visceral efferent group of cranial nerves and innervating muscles derived from the branchial mesoderm, each of these properties has been questioned. Consequently, the classification of the nerve is still unset tled. Evidence in support of a special visceral origin of the spinal XI nerve is found in the phylogenetic history of the spinal XI nucleus.

The traditional education of the neurosurgeon and duce simultaneous contrast preparations of the ar- the clinician working in related specialties is based teries and veins and thus obtain a complex photo- on their presumed knowledge of the macroscopic graphic representation of the structures of the prep- anatomy of the brain as traditionally taught. Most aration. neurosurgical textbooks, therefore, provide macro- The manuscript and drawings were completed in the scopic views of sections of the operative site. The years 1974-1976 after almost two decades of neu- literature that has accumulated in recent years on rosurgical work. The data worked out in the early the subject of microneurosurgical operations also stages (Chapter 1 in particular) were used by the follows this principle. author as the basis for teaching programmes at the For some years, however, the customary macro- University of Giessen. Chapters 2-7, dealing with scopic representation of the anatomy of the brain the operative technical aspects, were produced after has been inadequate for the needs of the neurosur- mid-1975 and used by the author as the basis for geon using refined modern operative techniques. microneurosurgical teaching of his colleagues at the Furthermore, despite their detailed presentation, University of Freiburg. stereotactic atlases are also insufficient for neuro- My thanks are due to Doz. Dr. E.

During development two strongly interrelated processes can be discerned in the central nervous system (eNS), namely morphogenesis and histogenesis. Most neuroembryological studies deal with histogenetic features virtually with- out any morphological elucidation. It must be stressed, however, that histogen- etic investigations should be based upon a thorough knowledge of morphogene- sis. This holds especially for the forebrain, which during development is sub- jected to drastic transformations, particularly when only two-dimensional sec- tions are used. Therefore the present study on morphogenesis forms the first part of a research project on the ontogenesis of the brain in the rhesus monkey. The second part (Gribnau and Geijsberts 1984) will deal with the early histogene- sis of the forebrain. The first recognizable precursor of the eNS in vertebrates is the neural plate, which, after the formation of the germ layers, is induced in the ectoderm. The lateral margins of the neural plate start to rise, forming a neural groove. Eventu- ally, they meet dorsally in the midline and fuse, resulting in the formation of the neural tube. The ultimate sites of closure at either end of the neural tube are called the anterior and posterior neuropores. Before the closure of the anterior neuropore, which precedes that of the posterior neuropore, the anlage of the eNS can be divided into a narrow elongated caudal part, the future spinal cord, and a wider rostral part, the precursor of the brain.

The Ornithopoda, one of five suborders within the Ornithischia, was originally proposed by Marsh in 1881 to include those bipedal dinosaurs possessing a predentary bone fitted over the rostral end of the mandibles. Ornithopods as recognized today can be further characterized by moderately long facial skele- tons equipped with well-developed, often toothless premaxillae and moderate to large external nares. Maxillary and dentary dentitions vary but usually consist of at least one replacement series beneath the functional set; some have many rows of successional teeth. Tooth morphology suggests ornithopods were suc- cessful herbivores but, as will be discussed, the precise way(s) in which ornitho- pods chewed their food, hence lending important information about their tro- phic position, has not been settled. Postcranially, ornithopods show specializa- tion for bipedality in hindlimb construction and lack well-developed protective structures on their flanks, back, and tail. The Ornithopoda can itself be divided into five families: Fabrosauridae, He- terodontosauridae, Hypsilophodontidae, 19uanodontidae, and Hadrosauridae (subdivided into the subfamilies Hadrosaurinae and Lambeosaurinae). Both fabrosaurids and heterodontosaurids, first known from the Late Triassic and Early Jurassic of Argentina and South Africa, were small animals differing in details of cranial, dental, and appendicular anatomy. Fabrosaurids are be- lieved to represent the basal ornithopod stock (Galton 1972, 1978; Thulborn 1970a, 1972). During the Jurassic, ornithopods underwent major radiations that included the medium- to large-sized Hypsilophodontidae and the large- bodied Iguanodontidae, both of which survived into the Cretaceous.

In 1953, at the grand age of 92, Ferdinand Hochstetter submitted his famous collection of photographs of human embryos entitled: "Uber die Entwicklung der Formverhaltnisse des menschlichen Antlitzes." Together with others papers, this contribution was published in 1955, a year after Hochstetter's death. In unbroken combativeness, Hochstetter discussed his results with regard to those of earlier embryologists and to those of his own lifetime. Thus, in an obituary, Elze (1956) reported about one of Hochstetter's letters from the year of his death (1954): "nur einige blodsinnige Behauptungen, die Fischel in seiner Ent- wicklung des Menschen verzapft hat, mochte ich vielleicht noch annageln," which may be translated as: "I would just like to pin down a few silly assertions that Fischel made in his Entwicklung des Menschen." In the first two paragraphs of his paper Hochstetter stated (in German, here translated freely): When I decided to write a detailed paper about the development of the morphology of the human face, too [in addition to a paper about morphology of the extremities in human embryos], I was especially moved by the fact that in none of the German manuals and textbooks on embryology known to me is there to be found a presentation of the development of the human face which could be considered - eveJ;l to a limited extent - rich in details, true, sufficiently illustrated, easy to understand by students as well as by scien-

Again rapid advances in the brain sciences have made it necessary, after only a few years, to issue a revised edition of this text. All the chapters have been reviewed and brought up to date, and some have been largely rewritten. The major revision has occurred in the chap ters on the autonomic nervous system and the integrative functions of the central nervous system. But in the discussion of the motor systems and other subjects as well, recent insights have necessitated certain conceptual modifications. In the description of the autonomic nervous system, the role of the intestinal innervation has been brought out more clearly than before. In addition, there is a new presentation of the physiology of smooth muscle fibers, and more attention has been paid to the postsynaptic adrenergic receptors, because of the increasing therapeutic signifi cance of the at f3 receptor concept. A substantial section on the genital reflexes in man and woman, including the extragenital changes during copulation, has also been added. The text on the integrative functions of the central nervous system has been expanded to include, for the first time, material on brain metabolism and blood flow and their dependence on the activity of the brain. Reference is also made to recent results of research on split brain and aphasic patients and on memory, as well as on the physiol ogy of sleeping and dreaming.

1. 1 Brief History The diversity of cells constituting the central nervous system did not deceive last century neurohistologists in recognizing that this organ contained essentially two cell types: the nerve cells, or as termed according to the emerging concept of neural contiguity, the neurons, and the neuroglial cells. Neurons were clearly shown to be the means of excitability, impulse generation, impulse transmission, and connectivity in the neural tissue. The neuroglia, as indicated by its name (YAloc=cement or glue) given by Virchow (1860), was thought to be the cement ing material ensuring the coherence of the nervous tissue, filling in the spaces of the neuropil, and isolating neuronal cell bodies. While this supposedly passive role did not attract multidisciplinary research on the neuroglia, successful efforts were made to extend our knowledge of the physiology, morphology, and bio chemistry of neurons. As a result of this, the investigation of the neuroglia carried out in the first half of this century was mainly confined to morphology, often as a by-product of comprehensive analyses of neuronal systems. At any rate, the histological classification of the neuroglia was accomplished, laying a framework which has been used to the present day. Accordingly, the glia was divided into two major groups: the macro- and microglia. The former comprises two further subclasses, the astroglia and oligodendroglia."

3. 11 Stage XI (ca. 10. 5-12. 5 mm) 48 3. 11. 1 Axial Relations 48 3. 11. 2 Lateral Relations 49 3. 11. 3 Summary . . . . 52 3. 12 Stage XII (ca. 13-16 mm) 53 3. 12. 1 Axial Relations 53 3. 12. 2 Lateral Relations 56 3. 12. 3 Summary 59 4 Discussion . . . . . 60 4. 1 Introduction 60 4. 2 Early Differentiation of the Somite Mesoderm 60 4. 2. 1 Dermatome . . . . 60 4. 2. 2 Myotome . . . . . . . . . . 61 4. 2. 3 Somitic Mesenchyme . . . . . 61 4. 3 Development of the Axial Mesenchyme 63 4. 4 Development of the Somitic Mesenchyme 66 4. 4. 1 Segmentation Process in the Somitic Mesenchyme 66 4. 4. 2 Differentiation of the Somitic Mesenchyme into the Mesenchymatous Primordium of the Axial Skeleton 70 4. 4. 2. 1 Metameric Condensations: Arcual and Costal Processes 70 4. 4. 2. 2 Axial Somitic Mesenchyme (Transverse Commissure) 73 4. 4. 2. 3 Perichordal Tube . . . . . . . . . . . . . . 74 4. 4. 2. 4 Linkage Between Lateral and Axial Segmentation 78 4. 4. 2. 5 Origin of the Mesenchymal Vertebral Bodies . . . 81 4. 4. 2. 6 Blastema of Vertebral Processes and its Relationship with the Blastemic Vertebral Body . . . . . . . . . . . . 83 4. 4. 3 Differentiation of the Somitic Mesenchyme in Relation to the Development of the Peripheral Spinal Nervous System 85 4. 5 Differentiation into Cartilaginous Axial Skeleton . . . . . . 89 . 4. 6 Differentiation of Myotomes; Morphology of the Developing Myotome . . . . . . . . . . . . . . . . . . . . . . . . 92 4. 7 The Notochord . . . . . . . . . . . . . . . . . . . . . 94 Some Remarks on the "Neugliederung" Concept with Special At 4."