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NOWOTWORY Journal of Oncology • 2007 • volume 57 Number 1 • 24e–33e Historia medicinae Evolution of the knowledge of electricity and electrotherapeutics with special reference to X-rays & cancer Part 2. Alessandro Volta to James Clerk Maxwell Richard F. Mould1, Jesse N. Aronowitz2 The first part of this article [1] recounting the history of electricity and of electrotherapeutics closed with the contribution of Charles Coulomb (1736-1806), Luigi Galvani (1737-1798), Pierre Bertholon (1742-1800) and Jean-Paul Marat (17431793). This second installment continues chronologically with the story with Alessandro Volta (1745-1827) and ends with Lord Kelvin (1824-1907) and James Clerk Maxwell (1831-1879). The concluding part (to be published in Nowotwory 2/2007), commences with Sir William Crookes (1832-1919) and closes with the electrotherapists of the early 20th century. By then, X-ray therapy and radium brachytherapy had replaced electrotherapy as the alternative to surgery in the treatment of cancer. Key words: electrotherapeutics, electricity, X-rays, cancer Alessandro Volta 1745-1827 Volta, professor of physics at the university of Pavia, found that the quantity of electricity necessary to evoke a convulsion in the legs of a freshly killed frog was minute, some 50-60 times less than that which could be detected by the most sensitive electrometer then available [2]. This nerve-muscle preparation, called by Volta the ‘animal electrometer’ was to be used to measure minute currents for some 30 years. Several years later he determined that the coupling of different metals generated a current, which was the electromotive force in Galvani’s frog leg preparation§. (Galvani had believed that the tissues themselves had generated ‘animal electricity’) Volta used this discovery in 1800 to construct the first source of electricity. The ‘voltaic pile’: a column of alternating discs of silver and zinc (or copper), separated 1 2 § 41 Ewhurst Avenue South Croydon Surrey CR2 0DH United Kingdom Department of Radiation Oncology University of Massachusetts Medical School Levine Cancer Center 33 Kendall Street Worcester MA 01605 USA The histories of Luigi Galvani and Alessandro Volta are intertwined. Part 1 in Nowotwory issue 2/2006 ended with Galvani (1737-1778). Figure 1. Volta’s pile. The dark layers in the piles in the centre and bottom of the figure are pieces of brine soaked cardboard. At the top of the figure is his ‘crown of cups’ (couronne de tasses), consisting of a series of cups containing brine or dilute acid. The cups are connected by compound strips, half zinc/half copper. The difference in potential between the first and the last cups is proportional to the number of pairs of metal strips. [3] (Courtesy The Wellcome Trust, London). 25 25e Figure 2. Volta demonstrating his pile to Napoleon in Paris, in 1801 (Courtesy The Science Museum, South Kensington, London). by cardboard saturated by a salt solution (Figure 1) which produced a constant current of electricity [3]. Later versions had the strips or discs of the dissimilar metals immersed in brine or in a weak-acid electrolyte. Figure 2 depicts Volta demonstrating his pile to Napoleon who, perhaps understanding the significance of the discovery, awarded him a gold medal and a pension. Within a few years other investigators were constructing piles and carrying out experiments. In 1800 the chemist William Nicholson (1753-1815) and the surgeon Anthony Carlisle (1768-1840) electrolytically decomposed of water into hydrogen and oxygen [4]. William Cruickshank (1745-1800) fashioned a more powerful pile of rectangular zinc and copper plates in a resin insulated wooden trough [4-6]. Then in 1801, William Hyde Wollaston (1766-1828) established the identity of voltaic currents with frictional electricity, by demonstrating that either can decompose water [7]. Humphry Davy 1778-1829 In 1806 Humphry Davy’s Royal Society Bakerian Lecture of [8] contained the first clear exposition of the mechanisms of electrolysis and of the voltaic battery [4]. Hans Christian Oersted 1777-1851 A relationship between magnetism and electricity had long been suspected. Lightening had been known to magnetise steel objects, but almost all attempts to duplicate these effects with electricity had failed. Then in 1820 a pharmacist in Copenhagen, Hans Oersted, demonstrated that a magnetic needle will orient itself at right angles to a nearby wire transmitting an electric current. This linkage of galvanism (current electricity) and magnetism provided a basis for the detection of the current by its magnetic effect. The instrument constructed on this principle was called a ‘galvanometer’ (which rendered Galvani’s ‘animal electrometer’ obsolete). André Marie Ampère 1775-1836 In 1821 the French mathematician Ampère discovered that current-bearing wires attract or repel each other. His investigations led to an elaborate theory and a science he labelled ‘electrodynamics’ to describe that part of the science which is concerned with this force. It is now known that these actions are purely magnetic and due to stresses in the intervening medium [9]. Following are the four laws of parallel and oblique circuits discovered by Ampère which form the basis of his theory. (1) Two parallel portions of a circuit attract one another if the currents in them are flowing in the same direction, and repel one another if the currents flow in opposite directions. (2) Two portions of circuits crossing one another obliquely attract one another if both the currents run either towards or from the point of crossing, and repel one another if one runs to and the other from that point. (3) When an element of a circuit exerts a force on another element of a circuit, that force always tends to 26e urge the other in a direction at right angles to its own direction. (4) The force exerted between two parallel portions of circuits is proportional to the product of the strengths of the two currents, to the length of the portions, and inversely proportional to the simple distance between them. Georg Simon Ohm 1787-1854 The mathematical formula stating the relationship between current, electromotive force, and resistance was the work of Georg Ohm. Ohm’s law states that the current in a circuit (i) is directly proportional to the electromotive force (E) and inversely proportional to the resistance (R). That is, i = E/R (in the CGS system E is measured in volts, R in ohms and i in amperes). Ohm published his findings in 1827 but his ideas were initially dismissed by his colleagues and he was forced to resign his modest teaching position at the Jesuit Gymnasium of Cologne. He lived in poverty for the next six years until he was offered a post as the Director of the Polytechnic School of Nüremberg. However, in 1841 the Royal Society in London recognized the significance of his discovery and the following year admitted him as a member. In 1854 he received his first professorship at a Germany university, of experimental physics at the University of Munich. interviewed Faraday and discovered that he was selfeducated, by reading the books he was binding. Davy offered him a temporary position, but by 1825 he had become Superintendent of the laboratory. In 1864 he was offered, but declined, the Presidency of the Royal Institution. In the 1830s, Michael Faraday studied the interaction of electric and magnetic fields and demonstrated that a moving magnetic field, or a fluctuating electric field, could induce a current in a nearby circuit: the principle of electromagnetic induction. These discoveries led to the invention of the magneto-electric generator (or dynamo) which uses a moving magnet to generate an alternating current. It also led to the induction coil which induces an alternating high voltage current from an interrupted low voltage current. The use of alternating currents in medicine became known as faradism, as distinct from galvanism which used continuous (direct) current generated by an electrochemical reaction. Figure 3 illustrates a textbook technique [10] of 1873 for ‘general Faradisation’. Figure 4 is an ‘apparatus for Faradization’ from a 1918 catalogue of electromedical and X-ray apparatus [11]. It depicts a device Michael Faraday 1791-1867 Faraday, a bookbinder’s apprentice, had the temerity to apply to Sir Humphry Davy in 1812 for a position as scientific assistant at the Royal Institution. Davy Figure 3. General faradisation in 1873 [9]. Figure 4. Apparatus for faradisation, advertised in a 1918 catalogue mainly containing X-ray apparatus. It was described as ‘Dr Spamer’s faradic battery’. A dry cell is included and an induction coil can be seen at the back and a selection of electrodes at the front. In front of the coil is an On/Off switch in front of which are three terminals, two of which are seen to be labeled P and S, for primary and secondary current. Batteries for galvanism were also sold by this company, with a choice of 20, 24, 28, 32 or 40 cells [11]. 27e Figure 5. The lettering on this 1824 oil painting by Edmund Bristow states ‘Medical electricity for the poor gratis from 8 till 10 in the morning. Cupping.‘ (Courtesy The Wellcome Trust, London). that combines galvanic and faradic electricity. That is, batteries with an induction coil in order to step up the voltage. This overcame the shortcomings of batteries (low voltage) and dynamos (low current). For comparison with Figure 3, Figure 5 is from the 1820s and shows a more graphic depiction of galvanism being given by an electrotherapist to his patient Electromagnetic induction led to the construction of the induction coil and transformer that produced the strong electrical currents of high voltage used by Röntgen and others when operating X-ray tubes. Figures 6-8 [12, 13]. Figure 6. This journalistic illustration in the April 1896 issue of The Windsor Magazine is a good likeness of Röntgen but there is an obvious error: the discharge tube is cylindrical, rather than the historically correct pear-shape [12]. Figure 7. X-ray tube electrical circuit (the batteries are not shown) in a German pamphlet of 1896. J = Insulator. R = X-ray tube. K = Photographic plate. O = Object to be X-ray photographed [13]. 28e system was used by Samuel Morse (1791-1872) who is credited with the invention of the telegraph although he knew of the earlier work of Henry.. Guillaume Duchenne 1806-1875 Figure 8. Induction coils advertised in 1901 in the Journal of the Röntgen Society. Many commercial companies sold these coils which were often referred to as Ruhmkorff coils after Heinrich Ruhmkorff (1803-1877). After working in Germany as an apprentice mechanic and in England with Joseph Brahmah (1748-1814), the inventor of the hydraulic press, he opened a shop in Paris in 1855 for the production of electrical apparatus. In 1858 he was awarded a 50,000 franc prize by Emperor Napoleon III for the most important discovery in the application of electricity, for a coil he built in 1851. Joseph Henry 1797-1878 Henry, the first Secretary of the Smithsonian Institution, was the leading American scientist after Benjamin Franklin. His chief scientific contributions were in the field of electromagnetism. He discovered the phenomenon of self-inductance. Oersted and others had observed magnetic effects from electric currents, but Henry was the first to wind insulated wires around an iron core in order to generate electromagnetism. Today, Faraday is recognized as the discoverer of mutual inductance (the basis of transformers) whereas Henry is credited with the discovery of self-inductance. Henry’s electromagnet made for Yale could lift 2,300 pounds and a later one constructed for Princeton could lift 3,500 pounds. It was at Nassau Hall, Princeton, that rigged two long wires one in front of and one behind the he building; demonstrating that he was able to send a signal by induction through the building. This was the earliest demonstration of wireless telegraphy. Also, whilst at Princeton, (for sending signals between his laboratory and his home) he used a system with a remote electromagnet to close a switch for a stronger local circuit. This was in effect an invention of the magnetic relay. A similar Duchenne was a pioneering neurophysiologist and one of the earliest physicians to employ faradism. His career began as a general practitioner in his home town of Boulogne but his fascination with electrotherapy led to self-education in electronics (he devised his own equipment), and his eventual relocation to Paris, to obtain a wider array of clinical material. Rather than seek a lucrative hospital appointment, he roamed the wards of Paris’s public hospitals, seeking neurological cases for his studies. At first considered something of an eccentric, his Paris colleagues eventually recognised him as a leading neuropathologist. Among his colleagues was the French neuropathologist Jean-Martin Charcot (1825-1893). Duchenne devised a technique, localised faradisation, consisting of nerve stimulation through moist electrodes, avoiding distress to the overlying skin. He dismissed franklinism, because the static charges largely remained on the skin surface and required painful sparks to stimulate the underlying nerves and muscles. He decried galvanism because the currents dessicated and cauterised the skin. An interesting application of faradism was its use to impede muscular wasting in degenerative diseases by means of electrical stimulation. He is recognised as the first who gave the definitive description with the clinical, electrical and pathological features of the disease now termed the Duchenne type of muscular dystrophy [15]. Duchenne photographed the stimulation of the facial expressions of emotions by electrical stimulation, demonstrating that the facial muscles of expression were grouped by individual nerves. The theory that the nervous system had evolved so that emotions could be expressed by a single nerve had been previously proposed by Charles Darwin (1809-1882). Duchenne’s 1856 experiments were performed upon mental patients in the Hôpital Salpêtrière. His principal subject ‘the old man’, was an ideal subject because he was afflicted with almost total amnesia, and allowed uncomfortable experiments to be repeated (Figure 9). This work was published in 1862 as The Mechanisms of Human Facial Expression [14, 15]. Carlo Matteucci 1811-1868 and Emil du Bois-Reymond 1818-1896 A professor of physics at Pisa, Carlo Matteucci, extending the work of Galvani, showed that an electric current accompanies each heart beat. He used a preparation known as a ‘rheoscopic frog’ in which the cut nerve of a frog’s leg was used as the electrical sensor and the twitching of the muscle as the visual sign of electrical 29e Figure 9a. Figure 9b . Figure 9. Duchenne with his electrodes applied to the face of ‘the old man’ (a). Example of eight facial expressions (b). (a Courtesy The Science Museum, South Kensington, London; b Courtesy The Wellcome Library, London). 30e Figure 10. First demonstration of cineradiography, 1896 [17]. activity [16]. In 1846 he invented they kymograph, used by physiologists for recording blood pressure. This would not be the last time that a frog’s leg woud be used as a test object. In 1896 John Macintyre (1857-1928), medical electrician at Glasgow Royal Informary, used a frog’s leg to demonstrate cineradiography (Figure 10) [17]. The German physician and physiologist Emil du Bois-Reymond (1818-1896) extended the experiments of Matteucci, demonstrating that muscles and nerves generate electrical currents. These physiological revelations provided a rationale for electrotherapeutics. Golding Bird 1814-1854 Golding Bird’s work on electrotherapeutics was influential during the 1830s, in part because he was both a physician and an electrician. His clinical work with galvanism, faradism, and static electricity was undertaken in the ‘Electricity Room’ at Guy’s Hospital, London. His subjects came from London’s lower working class population. A series of influential lectures on electrophysiology that Bird delivered to the Royal College of Physicians in 1847 drew a connection between biology and electricity, replacing the empirical use of electrotherapy with a rational one [18]. He kept detailed case histories on his patients: one such history was of a 15-year old girl with hysterical paralysis of the left side of her body following an ankle injury. Her neurological deficit was reversed by a two week series of daily electrical shocks from her sacrum to her toes. Robert Remak 1815-1865 Remak began his medical career as a neuroanatomnist; several neurological structures that he discovered are named after him. He had advanced the notion that cellular proliferation was due to division of pre-existing cells, and described (and named) the embryo’s three germ layers: he may well be considered the father of embryology. But academic advancement at the University of Berlin was denied because he would not renounce his Jewish faith. Embittered, he resigned his appointment and developed a second career, in electrotherapeutics. His neuroanatomy background was invaluable as a proponent of electrotherapy. He became dean of the German galvanists, which included Wilhelm Erb (18401921), a pioneer electrodiagnostician. Heinrich Geissler 1815-1879 and Johann Hittorf 1824-1914 Johann Heinrich Geissler was a German glassblower after whom the Geissler mercury pump, designed 1855, and Geissler tube are named. In 1854 he opened a shop in Bonn to make scientific apparatus. He produced glass tubes of many different complex shapes. Using his new pump, enough air could be extracted from his glass tubes to produce a relatively high vacuum, thereby improving upon available discharge tubes. An additional improvement was the use of platinum wire terminals, as the metal’s expansion when heated matched that of glass. Geissler produced luminous colour effects by applying high voltage currents from a Ruhmkorff coil (Figure 8) and admitting small quantities of various gases into his tubes. Two quotes from 1897 show the influence Geissler made on scientists. At the end of the 19th century it was stated ‘The beautiful glow of the Geissler tubes lent a fresh attraction to the study (of electrical discharges)’; and ‘Geissler tubes elicit glows of many colours, vieing in beauty with the fleeting tints of the aurora polaris’ [19]. One of the earliest types of quality control measurement with X-ray tubes consisted of simply looking at the colour of the glass bulb when X-rays were produced. Figure 11 is of a self-regulating X-ray tube manufactured by Queen & Company of Philadelphia before 1904 [20, 21]. The dark green colour (Figure 11a) was produced when the tube was operating at a low vacuum: a lighter green colour was observed when the tube was operating properly. The red colour (Figure 11b) was seen shortly after the tube had been punctured. The fluorescence depended on the type of glass of which the bulb was constructed. Glass in early tubes usually contained silicates of potassium, sodium and calcium; but sometimes also lead, manganese, aluminium and boron. 31e Figure 11a Figure 11 b Figure 11. Quality assurance by viewing the fluorescence of the glass of an X-ray tube. (a) A low vacuum produced the dark green colour. (b)When a tube was punctured the colour changed to red. These colour photographs appeared in textbooks of 1904 and 1907 [19, 20]. Most X-ray tubes of German origin fluoresced in yellow-green as they were normally made of potassium glass. Tubes manufactured in the United Kingdom were usually made of lead glass and fluoresced in blue [22]. Julius Plücker (1801-1868) was a mathematician and physicist who studied in both Germany and France. Using Geissler tubes he observed glass fluorescence in discharge tubes opposite one of the electrodes. He also observed cathode rays using a Geissler tube in 1859. Johan Wilhelm Hittorf (1824-1914), a student of Julius Plücker, made discharge tubes with a much higher vacuum, that either Plücker or Geissler. Using an Lshaped tube [23] he noted that the electrical discharge always occurred in the arm with the negative electrode. It was not until a few years later than Eugen Goldstein (1850-1930) used the term ‘cathode rays’ to describe the visible stream between the electrodes of excited vacuum tubes. Up to the early 1930s, X-ray physics books often introduced the subject with an explanation of a simple discharge tube and mention of Geissler (Figure 12) [24, 25]. Schall in 1932 describes the phenomena as follows [25]. ‘When the air in the tube is removed till the pressure inside falls to about 1/100th part of an atmosphere, so that the mercury column of a barometer would have dropped from 760 mm to 8 mm, the sharp-edged crackling sparks (Figure 12a) change to a furry noiseless caterpillar-like band (Figure 12b). At a pressure of 1 mm mercury the diameter of the discharge has increased, till the whole tube is filled with light. The resistance to the passage of electricity is much less, and a spark, which in air, would only just bridge a gap of 5 cm can discharge through a tube 100 cm long when the air pressure is thus reduced. This phenomenon was used by Geissler. When the pressure is still further reduced a dark patch, known as the Faraday dark space, surrounds the cathode (Figure 12c). At a yet lower pressure the luminosity of the tube breaks up into a number of bands known as striations, 32e whilst a second dark space appears round the cathode, known as the Crookes’ dark space (Figure 12d). When the pressure has fallen to 0.001 mm or thereabouts the dark space round the cathode fills the whole tube to the exclusion of all luminosity, but now the glass walls light up brightly with fluorescence. Hittorf in 1869 discovered that the dark space within the tube under these conditions is not merely an emptiness, but that there is evidence of rays which appear to come from the cathode and are therefore called cathode rays’. A much earlier illustration showing discharge patterns through an evacuated tube is seen in Figure 13, taken from the 18th century book by Abbé Nollet [26]. a b Lord Kelvin (William Thomson) 1824-1907 c d Figure 12. Discharge tube phenomena, after Schall [24]. 1, 2, 4, 7 – to air pump 3, 6 – Faraday dark space 5 – Crookes’ dark space Figure 13. Abbé Nollet’s discharge patterns through an evacuated tube [26]. William Thomson (elevated to Lord Kelvin in 1892) was a mathematical physicist and engineer who, in 1846 (at the age of 22) was appointed professor of natural philosophy at the University of Glasgow. In 1845 he gave the first mathematical development of Faraday’s idea that electric induction takes place through an intervening medium or ‘dialectric’ and not by some ‘action at a distance’. He also designed the quadrant electrometer to provide more accurate measurements of electric current and in 1851 gave a general theory of thermoelectric properties James Clerk Maxwell 1831-1879 The Scottish mathematician Maxwell, was a professor first in Aberdeen 1856-60, then at King’s College, London in 1860 and later in 1871, was appointed the first Cavendish professor of physics at Cambridge. He interpreted the earlier work of Faraday, Ampère and others, in terms of advanced mathematics forming a set of equations expressing the basic laws of electricity and magnetism. They are collectively known as Maxwell’s equations; they were first presented to the Royal Society in 1864. They describe the behaviour of both electric and magnetic fields, as well as their interaction with matter. Maxwell’s electromagnetic theory of light stated that light waves are not mere mechanical motions of the ether but are oscillations which are partly electrical and partly magnetic. The oscillating electrical displacements are accompanied by oscillating magnetic fields at right angles. In 1865 he wrote that ‘their velocity is so nearly that of light, that it seems we have strong reason to conclude that light itself (including radiant heat, and other radiations if any) is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws’ [27]. Maxwell then believed that the propagation of light required a medium for the waves, called the ‘ether’. Over time, the idea of the existence of such a medium in all space, yet undetectable by mechanical means, was abandoned. It was the work of Albert Michelson (18531951) that proved the non-existence of the ether. His 33e work culminated in the first Nobel Prize awarded to an American, for physics, in 1907. Hermann von Helmholtz 1821-1894 and Heinrich Hertz 1857-1894 12. 13. 14. In 1870 Hermann von Helmholtz derived the correct laws of reflection and refraction from Maxwell’s equations and, in 1881, posited the concept that charged particles within atoms would be consistent with Maxwell’s and Faraday’s ideas. He allowed for X-rays and radio waves in his theoretical dispersion theory of light, specifying their properties which included the power to pass through opaque material. He might therefore be considered to be the ‘theoretical discoverer’ of X-rays as distinct from Röntgen who was the experimental discoverer [28]. Von Helmholz’ first important scientific achievement was in 1847 in his physics treatise on the conservation of energy. Heinrich Rudolf Hertz, one of von Helmholz’ students, was the first to experimentally demonstrate electromagnetic radiation, showing that electric signals can travel through open air (as predicted by Maxwell and Faraday). This is the basis for the invention of the wireless. Hertz also worked on electric discharge tubes and observed that cathode rays could pass through a thin sheet of aluminium placed within the tube. In addition, he discovered the photoelectric effect when he observed that a charged object loses its charge more readily when illuminated by ultraviolet light. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. static and sinusoidal currents, Galvanism, cautery, thermo-therapy, radiotherapy, Faradism, light therapy, vibration. London: Watson & Sons; 1918, p 262.. Ward HS. Marvels of the new light. Notes on the Röntgen rays. Windsor Magazine April 1896; 3: 372. Dittmar A. Prof. Röntgen’s “X” rays and their applications in the new photography. Glasgow: F. Bauermeister; 1896. Duchenne GB. Mécanisme de la physiomomie humaine (ou Analyse électro-physiolopgique de l’expression des passions) . Paris: Renouard; 1862, English trans. Cuthbertson RA (ed.) The mechanism of human facial expression. Cambridge: Cambridge University Press; 1990. 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The early history of radiological physics: a fourth state of matter. Med Phys 1979; 6: 255-66. Mayneord WV. The physics of X-ray therapy. London: J & A Churchill; 1929. Schall WE. X-rays: their origin, dosage and practical application. 4th edn. Bristol: John Wright & Sons; 1932. Nollet, Abbé. Recherches sur les causes particulieres des phénoménes électriques. Paris : Freres Guerin, 1749. Maxwell JC. A treatise on electricity and magnetism. Oxford: Clarendon Press; 1873. Eisenberg RL. Predecessors of Roentgen. In: Eisenberg RL. Radiology an illustrated history. St. Louis: Mosby Year Book Inc; 1992, p 3-21. Paper received: 18 April 2006 Accepted: 9 July 2006 References 1. Mould RF, Aronowitz JN. Evolution of the knowledge of electricity and electrotherapeutics with special references to X-rays & cancer. Part 1. Ancient Greeks to Luigi Galvani. Nowotwory J Oncol 2006; 56: 653-62. 2. Volta A. 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Phil Trans Roy Soc London 1801; 91: 427-34. 8. Davy H. The Bakerian Lecture, on some chemical agencies of electricity. Phil Trans Roy Soc London 1807; 97: 1-56, read 20 November 1806. 9. Thompson S. Elementary lessons in electricity and magnetism. 3rd edn. London: Macmillan; 1918, (1st edn 1881). 10. Althaus J. A treatise on medical electricity. London: Longman; 1873, p 394. 11. Watson & Sons (Electro-Medical) Ltd. Price list [No. 228] of apparatus for radiography, high frequency, electrolysis, light, hydro-therapy, radioscopy,