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."

The testis is composed of seminiferous tubules and interstitial tissue. The most important component of the interstitial tissue are the testosterone-producing Leydig cells. The seminiferous tubules contain the successive generations of germ cells, which can only exist in the presence of Sertoli cells. Sertoli cells mediate the effect of testosterone, which is indispensable for the maintenance of spermatogenesis. Consequently, the function of the Sertoli cells depends large lyon the function of the Leydig cells, and a local control mechanism between the two cell systems has been assumed. Sertoli cells are supposed to interfere with the regulation of Leydig cell hormone production (Aoki and Fawcett 1978; Sharpe et al. 1981). Few cell types of the testis have received as much attention in recent years as have the Sertoli cells. While comprehensive data had accumulated concerning the differentiation of germ cells, there was formerly little information available on the influence of Sertoli cells on this process. Only through recently developed methods and experimental approaches could their central role in spermatogene sis be verified. Sertoli cells are the only somatic cells in the seminiferous tubules. Their origin is still disputed (for references see Ritzen et al. 1981). They supposedly stem either from the coelomic epithelium or from mesenchymal cells of the genital ridges. According to Wartenberg (1978) they are derived from a gonadal blas tema containing cells from both the coelomic epithelium and the mesonephros."

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-

Fish have adapted extremely successfully to the extremes of the aqueous environ ment, with the teleosts being outstanding in this respect. Amongst the class Pisces are pelagic species which must maintain certain swimming speeds in order to remain buoyant, species which migrate over thousands of miles, abyssal species living in waters with markedly reduced oxygen content, species living in the subzero waters of the Antarctic and also the obligatory air-breathing species of the tropics. Even in a comparatively benign environment such as the relatively shallow waters over continental shelves, the lifestyle of fish species varies greatly, with sedentary benthic and pelagic shoaling species coexisting within a comparatively narrow depth-range. Clearly, widely varying physiologi cal demands are made on species occupying such different environments and exhibiting such different lifestyles, and the successful provision of an adequate oxygen supply to the tissues is therefore of paramount importance to the fish. It follows that the demands made on the fish heart in irrigating the gill vascula ture will vary greatly according to the lifestyle and habitat of a particular species, and it is therefore surprising that authors reporting physiological, pharmacologi cal, biochemical and morphological investigations on the hearts of a consider able number of cyclostome, elasmobranch and teleost species imply that their results and conclusions can be extended to "the fish heart" in general."

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."

Of all cytoarchitectonic structures in the brain of mammals, the hippocampus is perhaps the most conspicuous because of its unusual macroscopic and micro- scopic appearance. During phylogeny, the hippocampus has developed from a single cortical plate in amphibia into a complicated, three-dimensional convo- luted structure in mammals. Because of its clear lamination into axonal, perikaryal, and dendritic layers, the hippocampus has often been considered a simple cortex model. Indeed, this trilaminated construction resembles perhaps the least complicated type of neuronal cortex. There is a large literature describing hippocampal morphology in many species with respect to cytoarchitectonics, fiberarchitectonics, angioar- chitectonics, chemoarchitectonics, synaptology, and fine structure. On the other hand, up to the present day there has been no generally accepted concept on the main functions of the hippocampus, although many studies dealing with its physiological and biochemical properties and its possible influences on behav- ior have provided some valuable indications. Early investigators described the hippocampus as being a part of the "rhinen- cephalon" (e. g. Zuckerkandl 1887), together with other allocortical structures, such as the olfactory bulb, olfactory tubercle, and piriform lobe. Thus, the hippocampus was assigned to the olfactory system, and it was not until improved degeneration techniques were applied that this error could be corrected. It be- came clear that only part of the allocortical areas receive direct olfactory inputs, namely the retrobulbar region (anterior olfactory nucleus), precommissural hip- pocampus, olfactory tubercle, prepiriform region, periamygdalar region, and part of the entorhinal region.

In the operation of reasoning, the mind does nothing but run over its objects, as they are supposed to stand in reality, without adding any thing to them or diminishing any thing from them. If I examine the Ptolomaic and Copernican systems, I endeavour only, by my inquiries, to know the real situation of the planets; that is, in other words, I endeavour to give them, in my conception, the same relation that they bear towards each other in the heavens. To this operation of the mind, therefore, there seems to be always a real, though often unknown standard, in the nature of things; nor is truth or falsehood variable by the various apprehensions of mankind. D. Hume, The sceptic. In: Essays. Moral Political and Literary. Oxford University Press, Oxford, 1963, p. 166. Contents 1 Introduction 1 2 Materials and Methods 2 3 Observations . . . . 4 3. 1 Topography of the Medial Geniculate Body 4 3. 2 Cytoarchitectonic Subdivisions of the Medial Geniculate Body 4 3. 3 Neuronal Architecture of the Ventral Division 7 3. 4 Structure ofAxons in the Ventral Division 21 3. 5 Cortical Connections of the Ventral Division 27 3. 6 Neuronal Architecture of the Dorsal Division 27 3. 7 Structure of Axons in the Dorsal Nuclei 39 3. 8 Neuronal and Axonal Architecture of the Suprageniculate Nucleus and the Posterior Limitans Nucleus . . . . . . 43 3. 9 Cortical Connections of the Dorsal Division . . . . . . 49 3. 10 Neuronal and Axonal Architecture of the Medial Division 56 4 Discussion . . . . . . . . . . . . . . . . . . .

Ever since the behavioral work of Lissrnann (1958), who showed that the weak electric discharges of some families of fish (hitherto considered useless for prey capture or for scaring away enemies) are part of a strange sensory system, these fish have attracted attention from biologists. The subsequent discovery of the electroreceptors in the skin of gymnotids and mormyrids (Bullock et al. 1961; Fessard and Szabo 1961) and the evidence that the ampullae of Lorenzini of nonelectric sharks and rays are also electro- receptors (Digkgraaf and Kalmijn 1962) was a start for a lively branch of physiological, anatomical, and behavioral research. Many fmdings of general importance for these fields have made the case to which extremes the performance of the central and peri- pheral nervous systems can be driven. Among those fmdings is the temporal accuracy of the pacemaker of some high-frequency fish which controls the electric organ, pro- bably the most accurate biological clock (coefficient of variation < 0. 0 1 %, Bullock 1982). The functional analysis of the pacemaker cells and their axons has established most of our knowledge on electrotonic synapses, the alternative to chemical synapses (Bennett et al. 1967), and of the implications of axonal delay lines for achieving extreme synchrony of parallel inputs to postsynaptic elements (Bennett 1972; Bruns 1971).

This monograph has attempted to bring together morphological and physiological studies of reptilian lungs, to analyze the nature of the resulting correlations, and to risk some speculations regarding the evolution of reptilian lung structure. Central to this work is the morphometric evaluation of the lungs in two species of lizard: "the teju (Tupinambis nigropunctatus Spix) and the savanna monitor (Varanus exanthema- ticus [Bosc]) which is presented here for the first time. These two species are similar in body form, and both are diurnally active predators, but their lungs are of basic- ally different structural types. The teju possesses relatively small, single-chambered (unicameral) lungs in which the homeycomb-like (faveolar) parenchyma is more or less evenly distributed along their length. In the monitor the lungs are large and many-chambered (multicameral), the individual chambers connecting to an unbranched, intrapulmonary bronchus. The parenchyma is in the form of shallow cubicles (ediculae), which are elaborated on the intercameral septa. The parenchyma is heterogeneously distributed within the lungs, tending to be most concentrated near the intrapulmonary bronchus and the middle third of the lung length. The ventral and caudal portions of these lungs are thin-walled and highly flexible. In both species those portions of the lungs which are most exposed to air convection possess dense capillary nets which almost completely cover both sides of the parenchymal partitions. In more distal regions of the parenchy- ma or of the lung, the intercapillary spaces become larger, creating a pseudo-single capillary net.

The study of the development of the spinal cord has a relatively long history. The spinal cord was singled out as a favorable site when cytological techniques were first applied to the study of the embryonic development of the nervous system. Bidder and Kupffer (1857), using the new procedure of hardening nerve tissue with chromic acid (Hannover 1844), made an investigation of spinal cord development in fetal sheep. They reported that the cellular central mass of the spinal cord develops before its fibrous envelope, deducing from this that the fibers of the white matter of the embryonic spinal cord were outgrowths of cells in the gray matter. Bidder and Kupffer also noted that in the spinal ganglia fibers grew out from cells in both directions, peripherally and centrally. Their report was one of the earliest ontogenetic lines of evidence in support of the later-formulated neuron doctrine (Waldeyer 1891). The spinal cord re mained a favorite topic of morphogenetic studies of the nervous system through out the last quarter of the nineteenth century, with seminal contributions made by His (1886, 1889), von Lenhossek (1889), Retzius (1898), and Ramon y Cajal (1960). Indeed, the preoccupation with the spinal cord in the early investigations of neural development had a lasting, and to some extent regrettable, influence on ideas about the ontogeny of the brain and on the terminology adopted by anatomists."

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Primary cortical areas receive a defmed input which makes them especially appropria- te for investigating cortical functions. The striate area is the only isocortical field which can be delineated unequivocally in the human brain. Nevertheless, there have been only a few morphological studies of this particular area (cytoarchitectonic studies: Bailey and Von Bonin 1951, Beck 1934, Von Economo and Koskinas 1925, Filimo- noff 1932; myeloarchitectonic studies: Sanides and Vitzthum 1965, Vogt and Vogt 1919; pigmentoarchitectonic studies: Braak H 1976, 1977). For Golgi impregnations, Ramon y Cajal (1900, 1909-1911), Conel (1939-1967), and Shkol'nik-Yarros (1971) preferred the incompletely myelinated material taken from brains of young childre- a fact that somewhat restricts their descriptions of the human striate area. Pigment preparations (Braak H 1978) provide a detailed view of the lamination of cortical areas. Furthermore, many types of cortical nerve cells reveal a typicallipofus- cin-pigment pattern (Braak H 1974a). Thus, a correlation can be drawn between the type of neuron as classified in Golgi preparations and the characteristic number and distribution of lipofuscin granules found in the cell body. Neurolipofuscin granules can therefore be considered the internal markers. In this study several cell types of the striate area have been identified under light and electron microscopes by means of their characteristic pigmentation.

In many aspects hematopoiesis in newborn rodents, especially in rats, resembles hema- topoiesis in the human fetus in the 6th-7th month of gestation. In man the transition from the stage of liver to bone marrow erythropoiesis takes place at this time (Bessis, 1973). In rodents, however, the liver is almost the only place where hematopoiesis occurs until birth. Thereafter it is replaced to a growing extent by the bone marrow, which so far consists mainly of immature mesenchymal cells (Maximow, 1910; Cuda, 1970). Thus hematopoietic precursor cells appear in the sternum only around 30 h after birth. Just as in premature human infants, a macrocytic anemia can be demonstrat- ed in normal neonatal rats (Lucarelli et aI., 1964, 1968). Beside liver (fetal) and bone marrow, the spleen is involved in hematopoiesis. In rodents like rats and mice, splenic hematopoiesis persists more or less markedly until adulthood; in man, however, it ceases after birth and reappears only under certain pathological conditions (Fischer et aI., 1970; Hennekeuser et aI., 1967; Fresen, 1960).

The octapeptide angiotensin II (ANG II, Fig. 1) is the key effector substance of the renin-angiotensin system (RAS) (Werning 1972, Page and Bumpus 1974, Hierholzer 1977, Vecsei et al. 1978, Johnson and Anderson 1980 lit. ). ANG II is formed in two enzymatic steps. Renin acts on renin substrate, a glycoprotein, to produce angiotensin I (ANG I, a decapeptide), which in turn is acted upon by converting enzyme to form ANG II (Skeggs et al. 1968, Fig. 1). Renin substrate (angiotensinogen) is produced mainly in the liver (Page et al. 1941) and is a constituent of the ~-globulin fraction in the circulating plasma (Plentl et al. 1943). The two enzymes involved in the formation of ANG II from renin substra- te are formed at various sites in the body. Renin (E. C. 3. 4. 99. 19) is produced mainly in the granular epithelioid cells of the kidney (Cook 1971, Taugner et al. 1979, Davi- doff and Schiebler 1981), and converting enzyme (CE, E. C. 3. 4. 15. 1) occurs chiefly in the lung (Ng and Vane 1967, Bakhle 1974 lit. ) as well as in numerous other tissues, such as the juxtaglomerular apparatus of the kidney (Granger et al. 1969, 1972) and the brush border of the renal proximal tubule (Ward et al. 1975, 1976; Ward und Erdos 1977). The biological effects of ANG II are numerous.

The aim of this investigation is threefold: (a) to determine the time of origin of neurons of the rat cranial nerve ganglia; (b) to reexamine the embryonic development of the cranial nerve ganglia in the light ofthese dating results; and (c) to attempt to relate the chronology of these peripheral events to developmental events in those nuclei of the medulla that are intimately associated with the cranial nerve ganglia. Although thymidine-radiography has been used for over 2 decades to investigate the time of origin of neurons, most of these studies dealt with central nervous struc tures. There are relatively few studies available concerning the birth dates of neurons in the peripheral nervous system. In fact, to our knowledge, there is only a single thymidine-radiographic report available dealing with the time of origin of neurons of a cranial nerve ganglion in a mammal; this is the recent study by Forbes and Welt (1981) of neurogenesis in the trigeminal ganglion of the rat. In the present study we determined the birth dates of neurons of the trigeminal, facial, vestibular, "glosso pharyngeal, and vagal ganglia of the rat. We utilized the progressively delayed com prehensive labeling procedure, a method which, in contrast to the single-pulse labeling procedure, allows the exact quantification of the proportion of neurons formed on a particular day."

In 1949, the Dutch anatomist Jan Boeke was able to write: "The socalled interstitial cells . . . which lie at the end of the sympathetic endformation as a connecting link between the nervous endformation and the effector cells, are . . . shown to be of pri mary importance for the transferring and the remoulding of the nervous stimulus . . . . " And: " . . . the problem of the interstitial cells and of the synapse is the most impor tant problem of neurohistology of the future. " When Boeke wrote this, he advocated the generalized concept, holding that inter stitial cells were intercalated between autonomic nerves and effector cells. A frank illus tration of this is presented by Tinel (l937), who places interstitial cells of Cajal (ICC) as terminal neurons of all autonomic nerves (his Fig. 1). While there have been over 100 light microscopic investigations (Table 1) of ICC in tissues and organs other than intestine, none of these have been followed up by electron microscopic studies. It is important to bear in mind that when the term ICC is used today, the only reference tissue for which sufficient information (i. e., including an ultrastructural identification) on the ICC is at hand is the intestine, or rather the muscularis externa of small inte stine (in Table 1, those contributions which relate to intestinal ICC are underlined)."

Of all the classes in the animal kingdom, birds represent the best known. There are in total about 8600 living species, and the systematic study of this class is more or less complete. Extensive observations - to a large extent by amateur ornithologists - with respect to geographical distribution, life cycles, demands on and adaptations to the environment, breeding habits, migration, and so forth have contributed towards basic and more widely relevant knowledge, e. g., in the areas of ethology, ecology, and evo lution and also in social biology (Hilprecht 1970; Farner and King 1971). Together, all these aspects are affected by the reproductive biology of birds, and studies have therefore been carried out for many years with special emphasis on this subject. How ever, until now this emphasis in avian reproductive biology has been physiological and in particular endocrinological (Murton and Westwood 1977; Roosen-Runge 1977). The morphology of the gonads has been treated in far less detail, and has been confined to a comparatively small number of species, compared with other classes of vertebrates. Reproduction is the section in the life cycle of an animal which is most dependent upon environmental conditions. Reproduction therefore usually takes place at a par ticular time, when stress for the adult animals is at its lowest and the chances of sur vival for the newborn are at their highest, i. e."

Over the past few decades an exceedingly large number of experimental and clinical investigations have been performed in an attempt to analyze the way in which the kidney functions. The basis for all this work was established during the nineteenth and the early twentieth century by morphologists (Bowman 1842; Hyrtl1863, 1872; Heidenhain 1874; Peter 1909; von Mollendorf 1930). All these investigators clearly outlined the extremely heterogeneous assembly of renal tissue and also defined the nephron as the smallest morphological unit. It was further the merit of these anato- mists and histologists to preclude quite a number of nephron functions based merely on their careful observations. Contemporary histologists have been able to add little to these observations. Unfortunately with the introduction of physiologic in vivo et situ studies on kidneys the interest in heterogeneity waned. This lack of attention was aggravated by the introduction of the clearance techniques which cannot account for regional differences in the function of the smallest unit, the nephron. That ana- tomic heterogeneity has a functional correlate was strongly suggested by Trueta et al. (1947) and vigorously stimulated a number of studies. The development of physiologic microtechniques, like micropuncture and microperfusion of single nephrons, or the perfusion of isolated nephron portions and electrophysiologic studies, enormously expanded our knowledge concerning details regarding nephron and total renal func- tion.

The present monograph is an imaginative and courageous attempt to provide a synthesis of knowledge concerning the af- ferent connections of the medial basal hypothalamus. Only somebody who has lived through most of the explosive develop- ment - over the last 25 years or so - in the neuroscience in general, and in hypothalamic functional neuroanatomy in parti- cular, can fully appreciate the remarkably consistent picture emerging from this study. The writer of this foreword was (alas!) an active participant in the very early and premature, and also largely naive, attempts to penetrate the "jungle" of hypothalamic connections with degeneration methods when they first became available in the late 1930s. (I have told a part of this rather pathetic story is an autobiographical sketch in Pioneers in Neuroendocrinology [Meites et aI. , (eds) (1975), Vol I. Plenum] because I was sufficiently self-critical not to publish my early results. ) Even with the suppressive Nauta-type silver stains, introduced in the mid-1950s, studies of hypothala- mic connections had only marginal results, which the reader will certainly appreciate if he compares the relevant figures in the first edition of Hypothalamic Control of the Anterior Pituitary [Szentagothai et al. (1962) Akademiai Kiad6, Budapest], with Dr. Zaborszky's concluding diagrams. The approach used by Dr. Zaborszky of combining the more advanced Fink-Heimer type degeneration techniques, and some of their most recent modifications by Gallyas et al.

The mature vertebrate retina is a highly complicated array of several kinds of cells, capable of receiving light impulses, transforming them into neuronal membrane currents, and transmitting these in a meaningful way to central processing. Before it starts to develop, it is a small sheet of unconspicuous cells, which do not differ from other cells of the central nervous system. The chain of events which lead to the trans formation from this stage into that of highly specialized cells ready to fulfll a specific task, is usually called "differentiation. " Originally, this word indicated firstly the proc ess of divergence from other cells which were previously alike, and secondly, the change from an earlier stage of the same cello lt has become widespread practice to imply by the word "differentiation" also the acquisition of specific properties and capacities which are characteristic of a mature, Le. , specifically active, cello Every cell is active at any stage of development, but certain activities are shared by most cells (e. g. , the activities of preparing and accomplishing proliferation, that of initiating development, that of maintaining a certain level of metabolism), while there are others which are shared by only a small number of - originally relate- cells. In most cases these latter activities are acquired by the fmal steps of cellular development, the terminal "differentiation. " In the context of the present paper, the word "function" will refer to this latter type of specific activity.

History of Anatomy: An International Perspective is unique in its global approach to studying the development of human anatomy. Though it references widely known anatomists, such as Aristotle, Galen, and Bell, the book also pay homage to less famous contributors to the field and explains their findings. This comprehensive history of the morphology of humans serves as a useful guide to anatomists, anthropologists, physicians, surgeons, and anyone interested in the early history of medicine and surgery.

Biopsy pathology of the lymphoreticular system has been written primarily for diagnostic histopathologists although we hope that other workers in the field of lymphoreticular disease will find it of interest and value. With our primary readership in mind we have generously illustrated most sections of the book. Allillustrationsare of haematoxylin and eosin stained sections unless otherwise specified. Conceptual understanding of the histogenesis and interrelationship of non-Hodgkin's Iymphomas has been in a state of turmoil for over a decade. In more recent years immunological and immunocytochemical studies have clarified some problems although in other areas such as the T-celllymphomas histogenetic interrelationships are still far from clear. We are aware, therefore, that in writing this book we have been aiming at a moving target; nevertheless, we feel that the need for such a book, particularly amongst diagnostic histopathologists, outweighs the advan tage of waiting until all the t's are crossed and all the i's dotted."

Anthropocentricity and pragmatism seem to be the main reasons why pigeons have served as the "black boxes" of so many psychologists and neurobehaviorists during the past decade. Anthropocentricity, because at first glance pigeons show several strik ing features which bear a beautiful similarity to human systems in respects such as drinking, bipedality, territoriality, and apparently easy pursual of individual interests. Pragmatism, because of the suspected lesser complexity of the pigeon's system, which enables them to serve as good paradigms for human systems. For example, the visually guided grasping system of the beak could be used as a model for the visually guided grasping system of the tips of the thumb and forefinger in humans (personal communi cation, Zeigler). Other pragmatic reasons are the low cost of breeding these birds, their easy adaptation to experimental conditions, and their obvious capacity for learning and remembering. Although a closer and more critical examination largely undermines the anthropomorphic arguments, this has not diminished interest in the pigeon. In many studies on sensorimotor and motivational processes of hunger, thirst, and learning, pecking and drinking behavior serve as the systems on which the outcome of different black box systems is measured. Clear examples of this application are found in McFarland (1964, 1965), Dawkins (1966), Dawkins and Dawkins (1973), Goodman and Schein (1974), Machliss (1977), and Zeigler, Levitt, and Levine (1980)."

In the past decennia nonhuman primates have been increasingly used for research purposes in various scientific fields. Much interest has been focused on this group of animals in general and on the rhesus monkey in particular because of its close phylo genetic relationship with man. In some fields of research, however, such as embryology and microscopic anatomy, much less attention has been paid to nonhuman primates, probably because of the expense involved in the collection of the extensive material needed. On the other hand, teratological and experimental embryologic studies must be based upon a thorough knowledge of the normal ontogenesis since only in that way can a reliable distinction be made between normal and abnormal or induced develop ment. Each ontogenetic study essentially consists of a comparison of different deve lopmental stages. In most reports dealing with the development of individual organs or their subunits the material used is classified according to the estimated age or the length of the embryos. These criteria, however, are not valid, since considerable varia tion in developmental stage occurs between animals of the same age even between littermates and between animals of the same length. Therefore a method is needed for assigning embryos to successive developmental stages that are defmed on the basis of extemal and internal characteristics. This type of classification was elaborated by Stree ter (1942, 1945, 1948,1951), who arranged human embryos into developmental hori zons numbered XI through XXIII."