Vision and the Dimensions of Nerve Fibers

Vision provided the obvious source of determining the dimensions of nerve fibers when suitable achromatic microscopes were directed at neural tissue in the 1830s. The earlier microscopes of Hooke and Leeuwenhoek were unable to resolve such small structures adequately. However, it was not Hooke’s microscope that led to an estimate of the dimensions of nerve fibers, but his experiments on the limits of visual resolution; he determined that a separation of one minute of arc was the minimum that could normally be seen. Descartes had earlier speculated that the retina consisted of the ends of fibers of the optic nerve, and that their size defined the limits of what could be seen. Estimates of the diameters of nerve fibers were made on the basis of human visual acuity by Porterfield in 1738; he calculated the diameters of nerve fibers in the retina as one 7,200^th part of an inch (0.0035 mm), based on the resolution of one minute as the minimum visible. In the same year, Jurin questioned the reliability of such estimates because of variations in visual resolution with different stimuli.     

Camillo Golgi on the Structure of the Hippocampus

Golgi's only paper on the pes Hippocampi major was published in 1883 and then reprinted and translated a number of times. In it he stated that the fascia dentata provided the best information available to date on how nerve fibers and nerve cells are related. Based on the revolutionary silver chromate method he had introduced a decade earlier, Golgi described two sources of axons from the fascia dentata: one consisted of direct axons from the granule cells, and the other consisted of indirect axons from a diffuse neural net or reticulum that was generated from collaterals of the direct axons. The same basic arrangement was described for Ammon's horn, but neither was illustrated, and it is important to bear in mind that this work was published before the ‘neuron doctrine’ and ‘law of functional polarity’ were elaborated in the 1890s.     

Camillo Golgi on the structure of the hippocampus

Golgi's only paper on the pes Hippocampi major was published in 1883 and then reprinted and translated a number of times. In it he stated that the fascia dentata provided the best information available to date on how nerve fibers and nerve cells are related. Based on the revolutionary silver chromate method he had introduced a decade earlier, Golgi described two sources of axons from the fascia dentata: one consisted of direct axons from the granule cells, and the other coonsisted of indirect axons from a diffuse neural net or reticulum that was generated from collaterals of the direct axons. The same basic arrangement was described for Ammon's horn, but neither was illustrated, and it is important to bear in mind that this work was published before the "neuron doctrine" and "law of functional polarity" were elaborated in the 1890's.     

Galen's ideas on neurological function

Galen was the leading physician of the Roman empire during the last half of the second century. Unlike some of his predecessors, Galen concluded that the brain controlled cognition and willed action. The initial evidence for this doctrine was that the brain was the site of termination of all of the five senses: touch, taste, smell, sight, and hearing. Galen presumed that the information from these five senses was organized by a part of the brain that generated a concept of an object common to all senses; this part of the brain he considered to be the area of common sense. Galen thought that he could differentiate sensory from motor nerves (not nerve fibers) by palpation. Sensory nerves were soft because they needed to be impressed with the essence of the object seen, heard, felt, smelled, or tasted. Motor nerve fibers were very hard because they needed to carry the force of the will from the brain to the muscles. Strong willed people had especially firm motor nerve fibers; hence, the modern term that a person with great bravery has 'nerves of steel'. Galen considered that common sense, cognition, and memory were functions of the brain. Personality and emotion were not generated by the brain, but rather by the body as a whole (or perhaps by the heart and liver). Galen's studies of respiration and of the recurrent laryngeal nerve solidified the knowledge that the brain, not the chest, was the site of the rational power that guides human behavior. This doctrine has continued from Galen's time to the present.     

Visual images in Luigi Galvani's path to animal electricity

The scientific endeavor that led Luigi Galvani to his hypothesis of "animal electricity," i.e., of an electricity present in a condition of disequilibrium between the interior and the exterior of excitable animal fibers, is reviewed here with particular emphasis to the role played by visual images in Galvani's path of discovery. In 1791 Galvani formulated his model of neuromuscular physiology on the base of the image of a muscle and a nerve fiber together as in a "minute animal Leyden jar." This was the last instance of a series of physical models that accompanied Galvani's experimental efforts in the search of a theory capable of accounting for the electric nature of nerve conduction in spite of the many objections formulated in the eighteenth century against a possible role of electricity in animal physiology.     

Sigmund Freud's contribution to the history of the neuronal cytoskeleton

In the summers of 1879 and 1881, while Freud was a research student in Ernst von Brücke's laboratory at the Institute of Physiology at the University of Vienna, he carried out an important though seldom remembered investigation on the internal structure of nerve fibers and cells. His contribution to this field is here examined in the context of the 19th-century debate regarding the existence of neurofibrils and of present views on the cytoskeleton. Freud was able to discern separate fine fibrils following straight courses within the nerve fibers, as well as concentric loops of striae surrounding the nuclei and converging towards the processes of the cell bodies in crayfish nervous tissue. He thus confirmed and extended observations made by Robert Remak almost 40 years earlier, which had remained controversial. Electron microscopy of the crustacean nervous system confirmed Freud's main points, which in turn vindicated those of Remak. Both researchers were looking at small bundles of microtubules, and thus they were among the first to picture the lacy intracellular framework that future cell biologists would call the cytoskeleton.     

Sigmund Freud's Contribution to the History of the Neuronal Cytoskeleton

In the summers of 1879 and 1881, while Freud was a research student in Ernst von Brücke's laboratory at the Institute of Physiology at the University of Vienna, he carried out an important though seldom remembered investigation on the internal structure of nerve fibers and cells. His contribution to this field is here examined in the context of the 19th-century debate regarding the existence of neurofibrils and of present views on the cytoskeleton. Freud was able to discern separate fine fibrils following straight courses within the nerve fibers, as well as concentric loops of striae surrounding the nuclei and converging towards the processes of the cell bodies in crayfish nervous tissue. He thus confirmed and extended observations made by Robert Remak almost 40 years earlier, which had remained controversial. Electron microscopy of the crustacean nervous system confirmed Freud's main points, which in turn vindicated those of Remak. Both researchers were looking at small bundles of microtubules, and thus they were among the first to picture the lacy intracellular framework that future cell biologists would call the cytoskeleton.     

实验室模拟硅酸盐质文物除盐控盐的可视化研究

针对目前广泛使用的材料吸附除盐和加湿喷雾控盐等方法对含盐硅酸盐质文物可能造成的损伤,采用扫描电子显微镜、电阻仪和高分辨摄影仪等实时在线记录具有显色性质硫酸铜溶液在吸附除盐和水雾控盐加湿干燥过程中文物内部盐带分布的变化。研究结果表明：吸附材料除盐法和表面喷雾控盐法均会加速样品内部盐离子的扩散迁移,在样品中形成双层或多层盐结晶带;所形成的盐结晶带与样品结构特性、盐溶液在样品中的运移和蒸发速率、加湿-干燥频率等因素有关,其中溶液毛细上升高度和样品透气性越好,以及环境温度和盐溶液浓度越高,加湿-干燥频率越快,样品内部的盐带分布变化越明显。材料吸附除盐和水雾控盐等方法加速了盐溶液在样品内部的扩散,促进多层盐带的形成。这些结果对于目前文物保护所采取的除盐控盐技术手段提出了新的挑战。     

“You've Got to Work on This Axon”: J. Z. Young and Squid Giant Axon Preparations in 20th-Century Neurobiology**

Employing and extending Hans-Jörg Rheinberger's analytical concept of epistemic things, this essay proposes one reason why squid giant axons, unusually large invertebrate nerve fibers, had such great impacts on twentieth-century neurobiology. The 1930s characterizations of these axons by John Zachary Young reshaped prevailing assumptions about nerve cells as epistemic things, I argue. Specifically, Young's preparations of these axons, which consisted of fibers attached to laboratory technologies, highlighted similarities between giant axons and more familiar ones via lines of comparative study common to aquatic biology. Young's work convinced other biologists that the squid giant fibers were, in fact, axons, despite their unusual fused (syncytial) structures, thereby promoting further studies, such as intracellular measurements, made possible by the fiber's size. Tracing direct relations between preparations of squid axons and broader interpretations of neurons as epistemic things, this paper renders an actors’ category, “preparations,” into an analytical one. In turn, it offers glimpses into how aquatic organisms shaped twentieth-century neurobiology and how local experiments can drive broader, disciplinary changes.     

Testing Area‐Scale Fractal Complexity (Asfc) and Laser Scanning Confocal Microscopy (LSCM) to Document and Discriminate Microwear on Experimental Quartzite Scrapers

Few microwear studies have been conducted on tools made from quartzite. Most rely on visual observation of microwear features using optical light microscopes and scanning electron microscopes. Quantification of microwear on quartzite tools is extremely rare, even though numerous methods to mathematically document surface roughness have been applied to other silicate tools. In this paper, laser scanning confocal microscopy (LSCM) was used to document surface roughness on four experimental scrapers made from two different subtypes of Mistassini quartzite that were used on either fresh or dry deer hide. Surface roughness data were analysed using area‐scale fractal complexity (Asfc). The results of this test case indicate that Asfc can effectively discriminate between the unused and used regions on the quartzite tools based on surface roughness, and that it can also discriminate between surface roughness produced by working dry versus fresh hides. Differences in the subtypes of Mistassini quartzite did affect surface roughness, but not significantly enough to prevent discrimination of the dry and fresh hide‐working tools. Although the use of the Asfc parameter for lithic microwear analysis requires further testing, these first results suggest it could be a reliable technique to mathematically document and discriminate wear patterns on archaeological quartzite tools.     

A Very Moderate Socialist Indeed? R. H. Tawney and Minimum Wages

R. H. Tawney has been placed alongside G. D. H. Cole and HaroldLaski as one of the most important contributors to British socialistthought this century. But, on the issue of poverty wages, Tawneywas circumspect and conventional. In supporting such a modestreform as the 1909 Trade Boards Act, he was concerned with pragmaticconsiderations. His two studies of chainmaking and tailoring,funded by the Ratan Tata foundation and carried out at the LondonSchool of Economics, show him to be more concerned with moderate(and, in his opinion, workable) policies rather than radicalideas. In order to prove the boards a success, Tawney exaggeratedtheir advantages. It can be argued that what was required toend low pay was not industry-based trade boards, but a nationalminimum wage based on an agreed living income. Whilst Tawneyrejected Beatrice and Sidney Webb's national minimum wage asbeing overly based at the subsistence level, he also dismisseda more generous minimum on the grounds that it might be abovewhat an individual trade could bear. Although Tawney's ideaswere highly influential, they were an inadequate guide to solutionsto the problems of low pay in the twentieth century.     

Visual thinking and neuroscience

After a consideration of visual thinking in science the role of such thinking in neuroscience is discussed. Three instances are examined - cortical column, retina, impulse - and it is argued that visual thinking is employed, though in different ways, in each. It lies at the core of neurobiological thought.     

Leo Amery's Imperialist Alternative to Appeasement in the 1930s

Leo Amery has long been seen as one of the leading figures inthe anti-appeasement movement. However, key aspects of his caseagainst government foreign policy are not addressed in previouswork. This article considers Amery's reputation pointing outthat it is problematic to characterize him as an ‘anti-appeaser’because he did not rule out concessions to Germany and was willingto see Germany dominate Central Europe. However, he differedfrom the government in advocating a Danubian economic bloc tocreate stability and satisfy some German desires. This flowedfrom Amery's imperialism and his economic nationalism. Meanwhile,he fervently opposed colonial concessions, believing that Germangrievances could only be satisfied in Europe. Considering whetherAmery was an ‘anti-appeaser’ or a ‘real appeaser’,the article analyses Amery's doubts over whether to supportNeville Chamberlain over the Munich agreement. It concludesthat although Amery disagreed with Chamberlain more on tacticsthan strategy, these alternative tactics were significantlydifferent from government policy. As such, aspects of the anti-appeasementcase should be seen as being more nuanced than previously recognized,and the imperialist dimension of it should be understood.     

The Laurentian world map with special reference to its portrayal of Africa

When the Jesuit missionaries began to work in China, they attracted the attention of the Chinese by introducing European knowledge. This is the context in which Jesuits such as Matteo Ricci, Giulio Aleni, Francesco Sambiasi and Ferdinand Verbiest made their Chinese‐language world maps. Sambiasi was a man of many talents. He was a tactful diplomat and a learned scientist. His world map shows him to be a skilful adapter of earlier knowledge, which he passed on to future generations. The six known copies of his map are in two versions, printed from two sets of wood blocks (c. 1639). A text at the top of one version explains why the world must be seen as a sphere, which demonstrates how these maps were meant to convince the Chinese public of European scientific findings.     

Assessing the level of visibility of cultural objects in past landscapes

Visibility is often understood to play a significant role in the placement of cultural objects within past landscapes. In recent years, GIS-based visibility studies have become popular as a method for assessing the role of views to and from sites and features. A significant drawback to these analyses is that they do not take into account how far an object can be clearly seen and recognized. A number of factors influence the visibility of objects, including the limits of human visual acuity, environmental effects such as atmospheric extinction, and the physical properties of object and surroundings. Current approaches that attempt to account for these influences focus on defining visual zones, but are limited because they do not directly address object size. A fuzzy viewshed approach, modified to account for target size, is suggested as a solution for assessing the level of visibility of cultural objects in past landscapes.     

The discovery of REM sleep

The impetus to pursue the study of ocular motility in sleeping adults was derived from a previous study conducted by the author on infants. He noted through visual observation alone that there was an approximate twenty minute interlude of complete ocular quiescence during each hour of sleep. This period of quiescence was termed 'No Eye Movement Period' or 'N.E.M. Period', and it was the intent of the author to ascertain what effect age would have on the distribution of N.E.M. periods during sleep. In the latter part of 1951, the first continuous all-night recording of ocular motility in sleep using a combined EEG and EOG technique was conducted on the author's eight year old son. Instead of N.E.M. Periods, what he found were aproximately twenty minute periods of vigorous ocular activity including saccadic-like eye movements. Although he ultimately termed these epochs as 'REM Periods', his initial intent was to name them 'Jerky Eye Movement Periods' or "JEM Periods'. Ironically, some three decades later he found that a mathematical measure of jerkiness was a better discriminator than velocity in distinguishing REMs from waking saccades. Kleitman, who was the thesis advisor, played the role of skeptic during the REM discovery and demanded unassailable proof of the existence of REM. His feelings had to be ambivalent inasmuch as the REM state, with its concurrent activated cerebral cortex, negated his own theory that sleep was a completely passive phenomenon.     

Enrico Sereni: research on the nervous system of cephalopods

This essay focuses on a paradigmatic moment in neurobiological studies of invertebrates: the research on the nervous system of cephalopods carried out by Enrico Sereni at the Naples Zoological Station between 1925 and 1931. Although he remained unknown on the historiographic scenario, probably due to his early death, he contributed to Italian science of the first half of the twentieth century. In my paper particular attention will be given to Sereni's study on the pigmentary-effector, neurohumoral, and peripheral nervous systems, since they also accounted for the historical foundation of the experimental vein that, through the years, would lead John Zachary Young, Sereni's follower, to the most well-known discovery of the giant nerve fibers.     

Neuro-anniversary 2002

Abstract

The impetus to pursue the study of ocular motility in sleeping adults was derived from a previous study conducted by the author on infants. He noted through visual observation alone that there was an approximate twenty minute interlude of complete ocular quiescence during each hour of sleep. This period of quiescence was termed ‘No Eye Movement Period’ or ‘N.E.M. Period’, and it was the intent of the author to ascertain what effect age would have on the distribution of N.E.M. periods during sleep. In the latter part of 1951, the first continuous all‐night recording of ocular motility in sleep using a combined EEG and EOG technique was conducted on the author's eight year old son. Instead of N.E.M. Periods, what he found were approximately twenty minute periods of vigorous ocular activity including saccadic‐like eye movements. Although he ultimately termed these epochs as ‘REM Periods’, his initial intent was to name them ‘Jerky Eye Movement Periods’ or ‘JEM Periods’. Ironically, some three decades later he found that a mathematical measure of jerkiness was a better discriminator than velocity in distinguishing REMs from waking saccades. Kleitman, who was the thesis advisor, played the role of skeptic during the REM discovery and demanded unassailable proof of the existence of REM. His feelings had to be ambivalent inasmuch as the REM state, with its concurrent activated cerebral cortex, negated his own theory that sleep was a completely passive phenomenon.