Introduction

Teotihuacán, one of the two largest urban centers in the pre-Hispanic New World, lies a short distance northeast of Mexico City. At its height, about a.d. 200–600, it had a population of 150,000 and controlled much of the central Mexico region (Bernal 1966; Millon 1973). At that time it must have been importing enormous quantities of raw materials, both to supply its own huge population and to fuel the widespread trade network that it dominated. This raises a number of questions about the mechanisms involved in the exploitation and transportation of these resources. It is important to determine the role played by the Teotihuacán state in procurement, the scope and stability of the networks that were established, and the effects of these networks on the political and economic structures of both Teotihuacán and the source regions.

The concept of ‘neurosis’ was coined by William Cullen, the Scottish physician, and appeared first in his Synopsis Nosologiae Methodicae (1769) and then in his First Lines of the Practice of Physick (1777). In studies published between 1835 and 1841 three followers of the German Romanticism have disagreed with this fact and attributed the term to Felix Platter, the Swiss physician of the Renaissance. This dissenting view, however, is based upon a misinterpretation of the term ‘functionum laesiones’, utilized by Platter in his treatise of practical medicine. For Cullen the term ‘neurosis’ was no more than a useful neologism with which to refer to ‘nervous disease’, a concept current in the medicine of his time. Its meaning then, vastly different from the one in usage nowadays, embodies a view of neurosis that had currency before its anatomoclinical re-interpretation.

That the term ‘nervous disease’ had originated a century before was common knowledge amongst the writers who modified it during the second half of the eighteenth century and a number of studies available during Cullen's time echoed views from a British tradition that had been started by Willis and Sydenham. Cullen stated in Synopsis (IV, p. 182) ‘Since the time of Willis, British physicians have grouped some diseases under the category of nervous’. The Swiss Simon André Tissot, reported in his Traité des Nerves et de leurs Maladies (1778) (written 10 years earlier): ‘Sydenham… was the first to remark on the protean character of the nervous disease and to suggest that its symptoms might result from a disturbance in nervous function’.

The physiopathological view, the other dominant trend in nineteenth-century scientificonatural medicine, developed as a modification of the anatomoclinical view which must be considered as the very foundation of the new medicine. Its novelty was to emphasize the ‘functional’, which had been neglected by the great French writers and their followers, and to study objectively clinical and pathological dysfunctions. Laín Entralgo has carried out a masterly study of the group of German authors (Wunderlich, Griesinger, Frerichs and Traube) who occupied themselves with the notion of dysfunction. They presided over the modification of the anatomoclinical view under the influence of dynamic and idealist views received from an earlier period of German medicine. The dynamic processes of old, rid of all speculative elements, adapted themselves to the new view: Naturphilosophie became Naturwissenschaft.

The preponderance of the German school should not conceal the fact that the French and the British also sponsored the physiopathological view. In the Paris of the early nineteenth century the only view that kept the notion of the ‘functional’ alive was the ‘heterodox’ doctrine of Broussais. The so-called ‘Physiological medicine’, although occasionally exaggerated, showed a commendable insistence on physiopathology. Its early demise did not prevent ‘Médecine physiologique’ from influencing both the orthodox French anatomoclinical view and the British physiopathological school. However the main origin of the latter must still be sought in the influential views of John Hunter who interested himself both in the experimental analysis of function and in its post-mortem concomitants.

Although the history of the concept of neurosis during the twentieth century can be said to be a direct continuation of the views of Charcot and Freud, it has created severe difficulties amongst historians; this problematic character partially results from the fact that it has been used as a battle ground by schools of thought such as the scientific-natural method, psychoanalysis and psychosomatic pathology. Over the years this has given rise to numerous attempts at reformulating the concept of neurosis, criticising its foundations and even eliminating it altogether.

Most authors agree on the usefulness of analysing the concept historically. In a meeting held in 1925, dedicated to a ‘Revision of the Problem of the Neurosis’, Oswald Bumke, a representative of the reaction of German academic psychiatry against psychoanalysis, stated:

Unfortunately Bumke did not undertake nor encourage anyone else to do any historical research. He simply iterated few commonplaces about the evolution of the concept and used them to support his personal views.

The anatomoclinical view provided the earliest conceptual foundation of scientificonatural medicine during the nineteenth century. This achievement of the anatomoclinicians Laín Entralgo has called the ‘copernican revolution operated by the concept of anatomopathological lesion’ for the anatomical lesion, until then less important than the symptom, became the very basis of medicine.

A confrontation therefore was inevitable between the new view, based on localization and a reduction to the anatomical level, and the concept of neurosis, related since its inception to general diseases and interpreted physiologically. This confrontation will be explored first in the work of Pinel who presided over the transition between the Enlightenment and the new views; then in relation to the period during which efforts were made to jettison the concept of neurosis culminating with Georget's fundamental revision; finally its evolution will be traced during the zenith of the anatomoclinical view, between Georget and Charcot.

Pinel's work as the starting point of the anatomoclinical view of the neuroses

Paris was the indisputable capital of anatomoclinical medicine during the early nineteenth century. The French revolution and the ensuing sociopolitical climate had done away with all existing medical institutions and brought into being new ones free from the burden of tradition. For about twenty years Philippe Pinel (1745–1826), imbued by the ideal of a new medicine, presided over the transformation. Remembered as one of the founders of psychiatry, it is less known that he also forged the link between the Enlightenment and anatomoclinical pathology.

Germany's odd position in European medicine during the early part of the nineteenth century stems partially from her support of romantic speculative medicine, or so-called Naturphilosophie, in a period during which other countries (e.g. Austria and Britain) had already adopted the anatomoclinical view initiated by the Paris school.

Therefore, before exploring the impact of the anatomoclinical view, an account will be given of the way in which the concept of neurosis was influenced by speculative pathology and by its rival doctrines. One of these was eclecticism and the other a collection of views that, after 1830, marked the transition from Naturphilosophie to the anatomopathological view.

Absence of the concept of neurosis in the work of the followers of ‘Naturphilosophie’

Naturphilosophie refers to a complex speculative movement that developed in Germany during the romantic period out of the idealist philosophy of Schelling; associated mainly with the southern German Universities, its sponsors produced numerous publications during the first three decades of the nineteenth century.

How important is Naturphilosophie to the historical study of the concept of neurosis? It could be speculated that the tendency amongst the romantics to ‘personalize’ nature – that led writers such as Ringseis to postulate a link between disease and sin – might also have affected the evolution of the neurosis, for example by suggesting a sui generis and personalized formulation of the concept. The search for historical precedence however is always a bad historiographic technique.

The limited extent of the stream of air in a wind tunnel, whether of open or of closed working section, imposes certain restrictions on the flow past an aerofoil or other body under test, and the determination of the magnitude of this interference is of considerable importance, since it is found that certain corrections must be applied to the aerodynamic characteristics of an aerofoil tested in a wind tunnel before they are applicable to free air conditions. This interference correction is independent of and additional to any correction which may be necessary to allow for the change of scale from a model aerofoil to an actual aeroplane wing.

The theory of the interference has been developed by Prandtl in his second aerofoil paper by considering the conditions which must be satisfied at the boundary of the stream. The continental wind tunnels usually have an open working section and the condition of constant pressure must be satisfied at the boundary of the stream. British wind tunnels, on the other hand, have a closed working section of square or rectangular cross section, and the boundary condition takes the form that the component of the velocity normal to the tunnel walls must be zero. This boundary condition can be satisfied analytically by the introduction of a suitable series of images of the model, and the interference experienced by the model is the induced velocity corresponding to the vortex systems of these images.

Circulation and vorticity.

The definition of the circulation round a closed curve in two dimensions (see 4·1) as the integral of the tangential component of the velocity round the circumference of the curve can be extended at once to the more general case of motion in three dimensions by removing the restriction that the curve must lie in a single plane. Also by dividing any surface bounded by this curve into a network by a series of intersecting lines it can be shown that the circulation round the curve is equal to the sum of the circulations round the elementary areas formed by the network.

The vorticity of a fluid element in two-dimensional motion was defined (see 4·3) as twice the angular velocity of the element. This definition is retained in the more general case of three-dimensional motion but the axis of rotation of the fluid element may now point in any direction. By following the direction of the axis of rotation of successive fluid elements it is possible to construct a curved line whose direction coincides at every point of its length with the axis of rotation of the corresponding fluid element. Such a line is called a vortex line.

The vortex lines which pass through the points of the circumference of a small closed curve C will form the surface of a vortex tube, of which the curve C is a cross section.

The aim of aerofoil theory is to explain and to predict the force experienced by an aerofoil, and a satisfactory theory has been developed in recent years for the lift force in the ordinary working range below the critical angle and for that part of the drag force which is independent of the viscosity of the air. Considerable insight has also been obtained into the nature of the viscous drag and into the behaviour of an aerofoil at and above the critical angle, but the theory remains at present in an incomplete state. The problem of the airscrew is essentially a part of aerofoil theory, since the blades of an airscrew are aerofoils which describe helical paths, and a satisfactory theory of the propulsive airscrew has been developed by extending the fundamental principles of aerofoil theory.

The object of this book is to give an account of aerofoil and airscrew theory in a form suitable for students who do not possess a previous knowledge of hydrodynamics. The first five chapters give a brief introduction to those aspects of hydrodynamics which are required for the development of aerofoil theory. The following chapters deal successively with the lift of an aerofoil in two dimensional motion, with the effect of viscosity and its bearing on aerofoil theory, and with the theory of aerofoils of finite span. The last three chapters are devoted to the development of airscrew theory.

An airscrew normally consists of a number of equally spaced identical radial arms, and the section of a blade at any radial distance r has the form of an aerofoil section whose chord is set at an angle θ to the plane of rotation. The blade angle θ and the camber of the aerofoil section decrease outwards along the blade. If the airscrew moved through the air as through a solid medium, the advance per revolution would be 2πr tan θ and this quantity would define the pitch of the screw. Actually this quantity will not have the same value for all radial elements of the blade and so it is customary to define as the geometrical pitch of the airscrew the value of 2πr tan θ at a radial distance of 70 per cent. of the tip radius. An airscrew rotates in a yielding fluid and in consequence the advance per revolution is not the same as the geometrical pitch and may in fact assume any value. The value of the advance per revolution for which the thrust of the airscrew vanishes is called the experimental mean pitch, and in many respects the characteristics of an airscrew are defined by the ratio of the experimental mean pitch to the diameter.

An ordinary propulsive airscrew experiences a torque or couple resisting its rotation and gives a thrust along its axis.