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The new generations of physicians are, to a large extent, unaware of the complex philosophical and biological concepts that created the bases of modern medicine. Building on the Hellenistic tradition of the four humors and their qualities, Galen (AD 129 to c. 216) provided a persuasive scheme of the structure and function of the cardiorespiratory system, which lasted, without serious contest, for 1,300 yr. Galen combined teleological concepts with careful clinical observation to defend a coherent and integrated system in which the fire-heart-flaming at the center of the body-interacts with lungs' air- pneuma to create life. Remarkably, however, he achieved these goals, despite failing to grasp the concept of systemic and pulmonary blood circulations, understand the source and destiny of venous and arterial blood, recognize the lung as the organ responsible for gas exchange, comprehend the actual events taking place in the left ventricle, and identify the source of internal heat. In this article, we outline the alternative theories Galen put forward to explain these complex phenomena. We then discuss how the final consequences of Galen's flawed anatomical and physiological conceptions do not differ substantially from those obtained if one applies modern concepts. Recognition of this state of affairs may explain why the ancient practitioner could achieve relative success, without harming the patient, to understand and treat a multitude of symptoms and illnesses.

This study aims to document the historical conceptualization of the inner ear as the anatomical location for the appreciation of sound at a continuum of frequencies and to examine the evolution of concepts of tonotopic organization to our current understanding. Primary sources used are from the sixth century BCE through the twentieth century CE. Each work/reference was analyzed from two points of view: to understand the conception of hearing and the role of the inner ear and to define the main evidential method. The dependence on theory alone in the ancient world led to inaccurate conceptualization of the mechanism of hearing. In the sixteenth century, Galileo described the physical and mathematical basis of resonance. The first theory of tonotopic organization, advanced in the seventeenth century, was that high-frequency sound is mediated at the apex of the cochlea and low-frequency at the base of the cochlea. In the eighteenth and nineteenth centuries, more accurate anatomical information was developed which led to what we now know is the accurate view of tonotopic organization: the high-frequency sound is mediated at the base and low-frequency sound at the apex. The electrical responses of the ear discovered in 1930 allowed for physiological studies that were consistent with the concept of a high to low tone sensitivity continuum from base to apex. In the mid-twentieth century, physical observations of models and anatomical specimens confirmed the findings of greater sensitivity to high tones at the base and low tones at the apex and, further, demonstrated that for high-intensity sound, there was a spread of effect through the entire cochlea, more so for low-frequency tones than for high tones. Animal and human behavioral studies provided empirical proof that sound is mediated at a continuum of frequencies from high tones at the base through low tones at the apex of the cochlea. Current understanding of the tonotopic organization of the inner ear with regard to pure tones is the result of the acquisition over time of knowledge of acoustics and the anatomy, physical properties, and physiology of the inner ear, with the ultimate verification being behavioral studies. Examination of this complex evolution leads to understanding of the way each approach and evidential method through time draws upon previously developed knowledge, with behavioral studies providing empirical verification.

By the 1890s, placental arrangements had been documented macroscopically in lizards and fishes, but placental studies on such species lagged far behind research on mammals. In 1891, the biologist Ercole Giacomini (at the University of Siena, Italy) published the first histological analysis of a reptile placenta. Focusing on a placentotrophic lizard (Chalcides chalcides) with a morphologically complex placenta, Giacomini documented the histological and cellular bases for placental nutrient transfer and gas exchange. In conjunction with a follow-up study in 1906, he demonstrated that placental structure is correlated with function and can vary dramatically between related species. Giacomini's work was highly influential in showing that placentation in lizards had converged evolutionarily on that of mammals, while establishing reptile placentology as a highly promising area for future research., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The historical relevance of Galen has always been very high and his works have exerted a profound influence on medical thought for more than 1,300 years. This could be the main reason why his surgical expertise is often neglected. This brief study focuses on the contribution of this distinguished physician to head and neck surgery and it shows that Galen's surgical experience is well documented in his work., (Copyright © 2017 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

In 1670, when president Perigny died, Bossuet was nominated by king Louis XIVthfor being the tutor of his first son, Louis de France (1661-1711) as the Great Dauphin, and he will hold this office, during ten years until 1680, within the crown prince's educational team managed by the formidable duke of Montausier. In that environment he was induced to write several books ; one of them entitled About knowledge of God and oneself, in his chapter II "About the body", depict - according to knowledges, ideas and prejudices of that time - the general anatomy and what will be later named physiology, the body functions, rather the animal than the human ones. He went over the main organs with their summarily descriptions and what he understood about their effects, and the main organic functions. This is the opportunity for understanding how the)6th century medical concepts were assimilated and translated by an unversed person though he was a great prelate, a great preacher and a great author.

The evolution of knowledge regarding the anatomy and physiology of the spleen throughout Antiquity and the Early Middle Ages is described, and general perceptions about this organ during different eras along this time line are presented. The original words of great physicians from the period of time stretching from Ancient Egypt to the Avicennan era are quoted and discussed to demonstrate how knowledge of the spleen has evolved and to present the theories that dominated each era. Furthermore, theories about illnesses relating to the spleen are reported, which show how this organ was perceived-in terms of its function and anatomy-during each era.

This paper underlines the importance of the Pseudo-Aristotelian treatise De spiritu for our knowledge of early Hellenistic anatomical and physiological theories. We claim that the treatise verifies reports on certain 4th- and 3rd-century conceptions and debates otherwise attested only in later sources, and offers invaluable information on otherwise unknown ideas and discussions. Our claim is based on ten case-studies in which we explore the relation between the views found in De spiritu and known to us from other ancient sources, regarding ten specific topics. Following the results of our case-studies, we argue that De spiritu should be dated to the early decades of the 3rd century BC, after the circulation of the doctrines of Praxagoras of Cos, but before the discovery of the central nervous system by Herophilus and Erasistratus.

Our knowledge regarding the anatomophysiology of the cardiovascular system (CVS) has progressed since the fourth millennium BC. In Egypt (3500 BC), it was believed that a set of channels are interconnected to the heart, transporting air, urine, air, blood, and the soul. One thousand years later, the heart was established as the center of the CVS by the Hippocratic Corpus in the medical school of Kos, and some of the CVS anatomical characteristics were defined. The CVS was known to transport blood via the right ventricle through veins and the pneuma via the left ventricle through arteries. Two hundred years later, in Alexandria, following the development of human anatomical dissection, Herophilus discovered that arteries were 6 times thicker than veins, and Erasistratus described the semilunar valves, emphasizing that arteries were filled with blood when ventricles were empty. Further, 200 years later, Galen demonstrated that arteries contained blood and not air. With the decline of the Roman Empire, Greco-Roman medical knowledge about the CVS was preserved in Persia, and later in Islam where, Ibn Nafis inaccurately described pulmonary circulation. The resurgence of dissection of the human body in Europe in the 14th century was associated with the revival of the knowledge pertaining to the CVS. The main findings were the description of pulmonary circulation by Servetus, the anatomical discoveries of Vesalius, the demonstration of pulmonary circulation by Colombo, and the discovery of valves in veins by Fabricius. Following these developments, Harvey described blood circulation.

Galen (129-217) was the ultimate authority on all medical subjects for 15 centuries. His anatomical/physiological concepts remained unchallenged until well into the 17th century. He wrote over 600 treatises, of which less than one-third exist today. The Galenic corpus is stupendous in magnitude; the index of word-entries in it contains 1300 pages. Galen's errors attracted later attention, but we should balance the merits and faults in his work because both exerted profound influences on the advancement of medicine and cardiology. Galen admonished us to embrace truth as identified by experiment, warning that everyone's writings must be corroborated by directly interrogating Nature. His experimental methods' mastery is demonstrated in his researches, spanning every specialty. In his life-sustaining schema, the venous, arterial, and nervous systems, with the liver, heart, and brain as their respective centers, were separate, each distributing through the body one of three pneumata: respectively, the natural, the vital, and the animal spirits. He saw blood carried both within the venous and arterial systems, which communicated by invisible "anastomoses," but circulation eluded him. The "divine Galen's" writings, however, contributed to Harvey's singular ability to see mechanisms completely differently than other researchers, thinkers and experimentalists. Galen was the first physician to use the pulse as a sign of illness. Some representative study areas included embryology, neurology, myology, respiration, reproductive medicine, and urology. He improved the science and use of drugs in therapeutics. Besides his astounding reputation as scientist-author and philosopher, Galen was deemed a highly ethical clinician and brilliant diagnostician., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

According to their writings, ancient Greek physicians had explored the anatomy of the heart. Although pre-Hippocratic medicine, which relied on religion and mysticism, has nothing more to present than implausible theories and speculations, younger physicians thanks to their animal dissections were able to depict the heart with detail. Hippocratic "On the Heart", Aristotle's, Herophilus', Erasistratus' and Galen's writings provide us with the necessary data to take a look at the anatomy of the heart as it was described back then. Despite of some confusing passages in their writings and some erroneous notions, the heart was described with relative accuracy. In the years after antiquity and in the Middle Age the only information about the anatomy of the heart could be derived from the ancient Greek works and only anatomists of the Renaissance managed to displace them. In this paper we present the knowledge of all known ancient Greek physicians about the heart, with emphasis on its anatomy., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

The article, on the biography basis, systematizes the scientific directions in the activity of Nicolas Steno as one of leading creators of first scientific revolution in medicine (XVII century) which overwhelmed anatomical physiological Galen concept. The works of Nicolas Steno considering anatomy of excretory glands, cardiac and skeletal muscles and brain white substance are presented in the context of antecedent development of anatomy, content of anatomical physiological Galen concept and in interrelationship with underlying works of number European anatomist of XVII century (William Harvey, Thomas Bartholin, Jan Swammerdam, Marcello Malpighi, Willis, etc.).

Since antiquity, heart function and the mechanism of blood circulation within the human body have been the focus of attention of scientists from different parts of the world. Over the passage of time, the theories and works of these scientists have resulted in the achievement of today's knowledge of circulation. The medieval Persian scholar, Al-Akhawayni Bukhari (?-983AD), is among the physicians who investigated both the anatomy and the physiology of the human body. Al-Akhawayni describes the mechanism of pulmonary circulation in his only extant book, "Hidayat al-Muta`llemin fi al-Tibb" (A Scholar's Guide to Medicine) with which he made a contribution to the development of knowledge regarding this mechanism in the medicine of the Islamic world. In this paper, Al-Akhawayni's viewpoints on anatomy and the function of the heart, its related vessels, and also pulmonary circulation will be briefly discussed., (© 2013.)

Albrecht von Haller was born in Bern on October 16, 1708 and studied medicine in Tubingen and Leiden. From the middles thirties on, and for seventeen years, he taught botany, anatomy and surgery at the University of Gottingen, where he founded the botanical garden, the institute of anatomy and the Royal Society of Science. His research included the study of Swiss flora, experimentation in human physiology and the investigation of vascular anatomy. One of his main scientific interests was how the human body functions, and he believed that it worked as an active organism characterized by its capacity for reaction to stimuli and impulses. In his work Icones anatomicae (1743-1756), von Haller minutely described the human arterial circulation. This scientist also investigated the properties of the nervous and muscular systems, in particular in terms of sensibility and irritability, and the development of embryos. Albrecht von Haller died in Bern on December 12, 1777.

The Czech anatomist and physiologist of the 18th century, Jirí Procháska (1749-1820), ranks among the major figures of Czech cultural history. Due to historical circumstances, the works of Jirí Procháska were published mostly in Latin and only some in German. However, given that only two of his works have been translated into Czech and one of them also partially into English, the results of his extensive research activities are currently unavailable not only to the international scientific community, but also to the Czech scientific community. Although his research reflected the time in which he lived and thus has been re-evaluated by later researchers, his achievements undoubtedly belong to the major intellectual heritage of Czech science and certainly deserve attention as such. It is therefore our duty not only to remember the work and legacy of Jirí Procháska, which significantly influenced the development of our knowledge, but also to try to critically assess his contribution in terms of today. The article surveys the important biographical events of Jirí Procháska's life, taking into account the importance of his research and teaching.

This study summarises the original medical information contained in the treatise On the Nature of Man by the Byzantine scholar Nemesius, Bishop of Emesa (4th century), written in ancient Greek. Nemesius' work had a strong impact on later Byzantine scholarship, as witnessed by a number of treatises on human body that followed under a similar or identical title. This review introduces and summarises some of the basic views of Nemesius and compares them with those of Galen, one of the major contributors to medical knowledge of antiquity, in order to see how Galen's theories on anatomy and physiology influenced Nemesius. We conclude that the medical information in the work of Nemesius reflects the high level of Byzantine medicine of the time, as well as deep influences from ancient Greek intelligentsia and Galen in particular.

In recent years, there has been a renewed interest in the study of white matter anatomy, both with the use of postmortem dissections and diffusion tensor imaging tractography. One of the precursors in the study of white matter anatomy was Raymond de Vieussens (1641-1716), a French anatomist born in Le Vigan. He studied medicine at the University of Montpellier in southern France, one of the most ancient and lively schools of medicine in Europe. In 1684 Vieussens published his masterpiece, the Neurographia Universalis, which is still considered one of the most complete and accurate descriptions of the nervous system provided in the 17th century. He described the white matter of the centrum ovale and was the first to demonstrate the continuity of the white matter fibers from the centrum ovale to the brainstem. He also described the dentate nuclei, the pyramids, and the olivary nuclei. According to the theory of Galen, Vieussens considered that the function of the white matter was to convey the "animal spirit" from the centrum ovale to the spinal cord. Although neglected, Vieussens' contribution to the study of white matter is relevant. His pioneering work showed that the white matter is not a homogeneous substance, but rather a complex structure rich in fibers that are interconnected with different parts of the brain. These initial results paved the way to advancements observed in later centuries that eventually led to modern hodology.

Pietro d'Abano is recognized as a leading figure in the early history of European medical faculties. Translator and scholar, he translated and commented in Latin the doctrines of Greek and Arab physicians and philosophers having an ambitious attempt, to reconcile the opposing views of Arab medicine and Greek natural philosophy. Moreover he was one of the first to claim, three centuries before Harvey, that the heart is the source of blood vessels.

Herophilus of Chalcedon (c. 330-250 BC) is famous as one of the leading figures in the development of medicine in Ptolemaic Alexandria around the first half of the third century BC. However, his medical science seems to have intrinsic continuity of thought with Hippocratic medicine. Herophilus followed the medical principle formulated in the Hippocratic treatise "On the Nature of Man," when he made his methodological pronouncement to the effect that primary parts of the human body should be perceptible by the senses. Herophilus rejected cardiocentrism, introduced by his teacher Praxagoras into the medical school of Cos, and returned to Hippocratic encephalocentrism, as represented by the author of the Hippocratic treatise "On the Sacred Disease." Herophilus differentiated between the faculties of the soul and the ones attributed to the nature. In his differentiation between these two faculties, Herophilus probably had in mind the Hippocratic conception of nature as specifically applied to the domain of the human body, as distinct from the soul. Herophilus' commitment to Hippocratic medicine is confirmed by his literary works on some of the Hippocratic texts. It is probable that Herophilus regarded himself as a more faithful successor than his teacher to the tradition of Hippocratic medicine. His anatomical research on the structure and function of the brain, motivated by his loyalty to the Hippocratic tradition, led him to innovative contributions to the development of medicine.

The 17th century was characterized by a real revolution in the field of scientific research due to the introduction of the experimental method, promoted by Galileo Galilei who was the most representative scientist of this period. Therefore, medical disciplines, particularly Anatomy, underwent innovative and deep changes shattering traditional culture and representing the background for the modern science. In this fermenting period, Tuscany played a significant role since numerous distinguished scientists were gathered by Medici Grand Dukes (especially Ferdinando the 2nd and Cosimo the 3rd) at Pisa University and at their court in Florence. Among them, it must be mentioned Giovanni Alfonso Borelli, creator of iathromechanics, Marcello Malpighi, founder of microscopic Anatomy, Francesco Redi, who denied the insect spontaneous generation, Nils Steensen who continued in Florence his anatomical studies on lymph nodes and salivary glands while setting also the bases of modern geology. Moreover, at the end of the 17th century, the anatomical wax modelling techniques arose and developed in Florence thanks to the work of Gaetano Zumbo (or Zummo), capable of creating some real masterpieces, still very well preserved and collected in the Museum of Natural Sciences "La Specola".

Gjuro Baglivi (1668-1707) is a Croatian medical doctor and natural philosopher who realised a relevant scientific career and an European fame during the time of scientific revolution, having worked in Rome as an associate and personal secretary of M. Malpighi, as a personal doctor of two popes and teaching medicine at the Sapienza University. Baglivi's life and works have been investigated thoroughly due to their historical and medical history aspects but his other scientific and philosophical views were touched upon only in principle. From the history and philosophy of science perspective I investigated the epistemic foundations of Baglivi's medical praxis and his anatomico-physiological theory as they were the results not only of his medical knowledge, medical practice and anatomical observations but they emerged from Baglivi's conceptualization of structure and function of human body in the context of natural history and, respectively, natural philosophy of that time. Baglivi wanted to establish medicine on experimental and empirical foundations and to point to the object and the purpose of medical study--the human body. By doing this, and despite being a proponent of iatrophysics, Baglivi clearly separated medicine from physical and mathematical sciences which flourished in the 16th and 17th century. As they were derivated with great cautiousness in philosophysing from his empirical observations and experiments, even in the faulty explanations Baglivi's conceptions hide an analyticaly correct cognitive flair.

This article proposes that one possible version of writing the biography of a scientific image might be to populate it densely with meaning by writing about the relations it entertains with things that themselves lie outside of it, thereby supplying it with a specific mode of existence, infusing it with vitality and thus transforming it into a potential object of biographical endeavour in the first place. Consequently, the article commences and ends with the same image that in the beginning appears to be a more or less meaningless photograph of a male left hand on which a bizarre drawing is superimposed. In the course of the article, this image is reanimated: the medical questions that led to the experiment in whose context the image was produced, as well as the applied experimental strategies and techniques, are closely investigated; in relating it furthermore to a series of other images and by reflecting its epistemic status, the very same image in the end of the article appears as something completely different: a part of a map of the cutaneous nervous system of a male subject around 1900.

Galen, besides being one of the most important and productive doctors and medical writers of Antiquity, was also a dedicated and efficient self-promoter. This paper uses characteristic examples to illustrate how Galen, according to his own writings, combined anatomical and physiological demonstrations with scientific discussion, polemics and a confident self-portrayal in his public appearances.

Leonardo da Vinci was a genius whose accomplishments and ideas come down to us today, five centuries later, with the freshness of innovation and the fascination of discovery. This brief review begins with a summary of Leonardo's life and a description of the most important works of art that he bequeathed us, and then concentrates on his last great challenge. There was a point at which Leonardo's passion for art gave way to the study of human anatomy, not only to improve his drawing but to go beyond what had been simply a representation of form to understand the underlying functioning. Among his many interests, we focus on his study of the heart and blood vessels, which he observed carefully in animals and human autopsies, and reproduced in drawings of great quality with annotations of astonishing acuteness. The experience that he had acquired from observing the flow of water in currents and around obstacles, and the conclusions that he drew concerning hydrodynamics, were central to his interpretation of the mechanisms of the heart and of blood flow, to which he devoted much of his time between 1508 and 1513. From these studies, immortalized in drawings of great clarity, come what are acknowledged to be the first hemodynamic records, in which Leonardo demonstrates the characteristics of blood flow in the aorta and great vessels and the importance of blood reflux and the formation of eddies in the sinus in aortic valve his assiduous and careful observations, and his subsequent deductions, Leonardo put forward detailed findings on hemodynamic questions that advanced technology has only recently enabled us to confirm.

Johann-Christian Reil (1759-1813) was a prominent German physician, anatomist, physiologist and a professor at the Universities of Halle and Berlin. Anatomic features named after him include the island of Reil (insula), Beau-Reil cross furrows, Reil's finger, the fillet of Reil, and Reil's triangle. In 1795, he founded the first German journal of physiology, Archiv für die Physiologie. Later, he would also be considered the founder of German psychiatry (the "German Pinel") and coined the term "psychiatry." In addition, he was a private confidante and physician to Johann Wolfgang von Goethe. Reil died in 1813 from typhus while treating soldiers wounded in the Battle of the Nations at Leipzig during the Napoleonic Wars.

Aristotle is principally known as a theoretical philosopher and logician but he was also an eminent natural scientist. In particular, he should be considered probably the first anatomist in the modern sense of this term and the originator of anatomy as a special branch of knowledge. Although it seems certain that he did not perform dissections of human adult cadavers, he examined human fetal material and, above all, made systematic analysis of animal bodies. His contribution to comparative anatomy, as well as to human anatomy, was enormous. He founded the anatomical discipline on precise descriptive and scientific ground. He also coined a series of technical terms, which are still in use in the modern nomenclature. His observational skill was astounding. Although many of his physiological concepts turned out to be wrong, still his structural description of organs and body parts was often first-rank. The present study will chiefly focus on Aristotle's anatomical work and will provide only essential mention of his complex physiological and philosophical doctrine. The main purpose of this article is indeed to offer to today's anatomists a systematic account of the extraordinary achievements of this great pioneer of our discipline., (Copyright 2006 Wiley-Liss, Inc.)

William Harvey has long been celebrated as the founding father of physiology for refuting Galen and demonstrating that blood circulates round the body. Yet after his training at Padua, he became a committed Aristotelian: although strongly influencing the new observational sciences of the seventeenth century, Harvey himself looked back towards the classical past.

Wilhelm Waldeyer was anatomist, physiologist, and pathologist during the German Empire (the so-called Second Reich). His scientific career left many traces still noticeable today. Not only is he commemorated in "his" pharyngeal lymphoid ring and other eponyms, but he also coined an impressive range of successful medical terms, including "chromosome" and "neuron." Moreover, Waldeyer left truly physical traces by donating parts of his body to his own Institute of Anatomy in Berlin. His scientific production does, however, also include "pseudoscientific" works, notably his questionable research on African brains.

The rete mirabile, a vascular network assumed to give origin to the intracranial segments of the internal carotid arteries, was interpreted by Galen as the key station for the conversion of the "vital spirit" into the "animal spirit." According to this interpretation, the rete was determinant either in sustaining the cerebral functions, or in controlling the reproductive process in humans. This belief was a firm point of the medical doctrine for centuries, accepted by the Islamic and Christian scholars of the Middle Ages. The new anatomy of Vesale, though having stated that the rete does not exist in humans, was unable to settle the discussion on its actual occurrence and function because it could not provide an alternative hypothesis on the mechanisms of support of the cerebral functions. Uncertainties still lasted in the late 17th century, when progress in knowledge on the circulation of blood and the minute anatomy marked the beginning of the new era in the medical science.

Jan Ursinus was a continuator of the medieval Latin tradition of the glossed medical literature, which in his works was limited to anatomy only. Polish glosses can be considered equivalents to Latin and Greek names and only sometimes we can meet some wider and especially precious polish commentaries. Numerous quotations from works of other authors prove that Ursinus knew a lot of antique and contemporary authors. He described functions of several organs and was acquainted with fundamentals of medicine. Ursinus demonstrated to be good creator of the Polish anatomic terms and his work has been appreciated both in his times and nowadays.

The Leipzig anatomist and physiologist Ernst Heinrich Weber had introduced physiological thinking in anatomy and exact methods of mathematical physics to the study of the functioning of the body making him the founder of a physically orientated physiology. But he would not have been that excellent physiologist without being a nonetheless distinguished anatomist since he solved his physiological problems usually following function in close relation to structure. Together with his brother Wilhelm Eduard Weber (1804-1891), who later was to become a famous physicist, in their theory of waves he laid the basis for an exact analysis of the movements of fluids in elastic tubes und was the first to apply the basic laws of hydrodynamics to the circulation of the blood. In collaboration with his youngest brother Eduard Friedrich Wilhelm Weber (1806-1871), who worked as a prosector at his institute and together with Wilhelm Weber had studied the mechanics of the walking apparatus, he demonstrated the inhibiting effect of the vagus nerve on the action of the heart. Ernst Heinrich Weber's approach to consider an organ as a whole not neglecting the study of its function set him apart from most of his contemporaries and has characterized the work of the Leipzig anatomists and physiologists since his time. Among those was Wilhelm His from Basle who succeeded him in the chair of anatomy in 1872. On the basis of a systematic analysis of human embryos by means of serial sections and plastic reconstruction His completely reformed the field of embryology and was the first to present a comprehensive treatise on human embryology. The making of modern human embryology was, above all, his achievement. He did not confine himself to mere description but wanted to gain deeper insight into the causal events by developmental-mechanical conceptions. With his detection of the neuroblasts and that they give rise to an axon and later to dendrites His provided the developmental foundations for the neuron-theory.