Imagine you are sitting in a boat on a broad river, looking at a book that is a collection of electrocardiographs (or a tablet that has a electronic version of the same book). The river at this point has arisen from a number of tributaries that you cannot see, or may not be aware of. The body of knowledge about the nature, recording and interpretation of the electrical activity in the heart (i.e. a electrocardiograph) that you rely on, and take for granted, is also the result of the merging of different streams of knowledge.
While knowing the timelines of the electrocardiograph (ECG) is not essential for “reading” an ECG, an awareness of some the past developments helps us to appreciate the technical and scientific achievements that are the basis of the tracing in our hands. "Back to the Future" is a series of musings on some of the more interesting or important timelines.
Dynamism of the Human Body
As the clinical application of electrocardiography was evolving during the first decade of the twentieth century an Italian avant-garde art movement (Futurism) was also developing. Filippo Tommaso Marinetti published "The Founding and Manifesto of Futurism" in 1909 in the French magazine Le Figaro. The Futurists took speed, technology and modernity as their inspiration - they wished to destroy older forms of culture and to demonstrate the beauty of modern life: the beauty of the machine, speed, violence and change.
The Futurists strove to have their paintings evoke all kinds of sensations - and not merely those visible to the eye. They were fascinated by chrono-photography, a predecessor of animation and cinema that allowed the movement of an object to be shown across a sequence of frames. This influenced their approach to showing movement in painting, encouraging an abstract art with rhythmic, pulsating qualities.
One of the Futurists was painter and sculptor Umberto Boccioni (1882-1916), who painted Dynamism of a Human Body in 1913. This painting appeared on the cover of the Journal of the American Medical association (JAMA) in 2012. In that issue of JAMA Janet M Torpysaid this aboutthe painting: ”The colours and shapes within Dynamism of a Human Body resemble a child's simple pin wheel with its swirl of motion and hues. Separation of each segment within the painting, typical of divisional and Futurist works, adds to, instead of detracting from, the overall impact of life, creation, and birth. Intense colours and the impression of movement lend emotional energy to the painting, consistent with the violence and upheaval emerging from the Futurist manifestos. Right angles and corners formed by intersecting strong lines contrast with the bursting curves and near-abstractions, and blend with Boccioni’s tidy brush-work, visible just as he executed".
There are clear parallels between the chrono-photography of Futurism and the photography of a pulsating quartz string that was the basis of the images produced by the string-galvanometerin the early years of the twentieth century.
The Making of the Microscope
I Can See for Miles
You thought that I would need a crystal ball to see right through the haze
Well, here's a poke at you
You're gonna choke on it too
You're gonna lose that smile
Because all the while
I can see for miles and miles
I can see for miles and miles
Written by Peter Townshend and released in 1967 by The Who on their album The Who Sell Out
The ability of a small piece of polished glass that bulges at the centre and is thinner at the ends (a convex lenses) to magnify (and to concentrate the sun’s rays to a point that caused burning) has been known for centuries. Aristophanes in his play The Clouds (5th century BCE) mentions a burning glass. The Nimrud lens in the British Museum dates from about 750-710 BCE. It is an oval rock-crystal that has been ground and polished, with one surface plane and the one surface slightly convex. It has been regarded as an optical lens, but it is more likely that it is a piece of inlay, perhaps for furniture.
The use of a convex lens to form an enlarged/magnified image is discussed in the Book of Optics by the medieval Arab scholar Ibn al-Haytham in the 11th century. ‘Reading stones’ came into use between the 11th and 13th centuries; they were made by cutting a glass sphere into half and laying the sphere directly on paper to enlarge words and images. It was not until the last few decades of the 13th century that convex lenses were fitted into metal frames specifically to help people with defective vision.
The correction of the vision of people with myopia (difficulty seeing distant objects clearly) requires concave lenses i.e. lens that are thicker at the ends and thinner in the middle. These are more difficult to grind than convex lenses, but were on sale in Florence in 1451.
In the early 17th century (between 1604 and 1608) telescopes were created by putting the weakest available concave lens at one end of a tube, and the strongest available convex lens at the other end of the tube. Galileo Galilei created his first telescope in 1609, and used the same principles to make a magnifying device with a bi-convex objective and a bi-concave eyepiece.
About the time Galileo made his first microscope the eccentric Dutch inventor and engineer Cornelius Drebbel (1572-1633) was also constructing and selling his own microscopes. These had a crucial innovation: a three-piece extensible brass tube with a small plano-convex lens as the objective lens and a double-convex lens at the ocular lens. In 1624Galileo came across a microscope based on Drebblel’s design, and developed an occhialino (little eye) that had three bi-convex lenses and could magnify objects about 30 times. In 1625 Johannes Faber, in a letter to Federico Cesi, wrote “I should also mention that I am calling the new occhiale for looking at minute things a microscope.”
The Pioneer Microscopists
Hold, as 'twere, the mirror up to nature
William Shakespeare Hamlet (ca. 1600)
The names especially associated with early microscopic observations are those of Hooke and Grew in England, Malpighi in Italy, and Swammerdam and Leeuwenhoek, both in Holland. Their microscopes were imperfect, and were of two kinds: simple lenses, and lenses in combination, forming what we now know as the compound microscope.
Robert Hooke (1635-1703 ) In 1655 Hooke was employed by Robert Boyle to construct a air pump. Five years later, Hooke discovered his law of elasticity, which states that the stretching of a solid body (e.g., metal, wood) is proportional to the force applied to it. In 1662 he was appointed curator of experiments to the Royal Society of London. He suggested that the force of gravity could be measured using the motion of a pendulum (1666) and attempted to show that the Earth and Moon follow an elliptical path around the Sun. He stated the inverse square law to describe planetary motions in 1678, a law that Newton later used in modified form. Hooke complained that he was not given sufficient credit for the law and became involved in bitter controversy with Newton.
In 1665 Hooke published a book of observations with a two lens compound microscope. The book was called Micrographia. In this book he wrote "From Tis not unlikely, but that there may be yet invented several other helps for the eye, at much exceeding those already found, as those do the bare eye, such as by which we may perhaps be able to discover living Creatures in the Moon, or other Planets, the figures of the compounding Particles of matter, and the particular Schematisms and Textures of Bodies.”
Some of his illustrations are shown in Figure 4 and Figure 5
The Anglo-Irish satirist Jonathan Swift wrote in 1733:
"So naturalists observe, a flea
Has smaller fleas that on him prey;
And these have smaller fleas to bite 'em.
And so proceeds Ad infinitum.
Thus, every poet, in his kind,
Is bit by him that comes behind."
One of the best known of Hookes' observations involved cork, and the introduction of the term “cell.”
"Of the Schematisme or Texture of Cork, and of the Cells and Pores of some other such frothy Bodies.
I took a good clear piece of Cork, and with a Pen-knife sharpen'd as keen as a Razor, I cut ….. an exceeding thin piece… [which was placed]…….on a black object Plate.
I could exceeding plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular; yet it was not unlike a Honey-comb in these particulars.
First, in that it had a very little solid substance, in comparison of the empty cavity that was contain'd between, ……for the Interstitia, or walls (as I may so call them) or partitions of those pores were neer as thin in proportion to their pores, as those thin films of Wax in a Honey-comb (which enclose and constitute the sexangular celts) are to theirs.
Next, these pores, or cells, were not very deep, but consisted of a great many little Boxes…. the substance of Cork is altogether fill'd with Air, and that that Air is perfectly enclosed in little Boxes or Cells distinct from one another.
……. the whole mass consists of an infinite company of small Boxes or Bladders of Air"
Nehemiah Grew (1641-1712) was one of the first naturalists to use a microscope to studyplant morphology. Grew was a doctor by profession, receiving his degree in 1671. He practiced medicine in London where he met John Wilkins, one of the founders of the Royal Society. Grew was later engaged by the Royal Society to study plant anatomy.
Grew was guided by the idea that there may be similarities of function between animals and plants. He believed in the circulation of sap, in analogy with William Harvey’s discovery of the circulation of blood in animals, and he believed in a form of respiration in plants.
Jan Swammerdam (1637-1680). Despite a scientific career that lasted only a dozen years, Swammerdam was one of the outstanding comparative anatomists of the seventeenth century. His most remarkable work was in the field of insect anatomy, which he undertook in order to disprove Aristotle's claims that insects lack internal anatomy, develop by metamorphosis (sudden and complete transformation) and arise from spontaneous generation. By refining his techniques of microdissection and injection to the point where he could use them on the smallest and most delicate anatomical parts, Swammerdam was able to illustrate for the first time the complex internal structures of insects, including their reproductive organs; and to demonstrate the gradual development of an insect's adult form throughout all its larval stages.
Swammerdam was the first (in 1658) to observe and describe blood corpuscles in the blood of the frog. It was not until fifty-seven years after his death that his observations were published by Boerhaave, and, therefore, he did not get the credit forthis discovery.
Marcello Malphigi (1628-1694) trained as a medical doctor and was one of the first to use the microscope to study embryology. In De formatione pulli in ovo (published in 1673), he described the aortic arches, the neural groove and the cerebral and optic vesicles. He also described the red blood corpuscles, the Malpighian layer of the skin, the structure of the liver, the kidneys and the spleen. His greatest contribution to science was the description of the capillaries in the lungs (De pulmonibus, 1661).
“……. the blood is driven in very small [streams] through the arteries like a flood into the several cells, one or other branch clearly passing through or ending there. Thus blood, much divided, cuts off its red colour, and, carried round in a winding way is poured out on all sides till at length it may reach the walls, the angles, and the absorbing branches of the veins.
….. it can be inferred that that network which formerly I believed to be nervous in nature .... is really a vessel carrying the body of blood thither or carrying it away.”
Antony van Leeuwenhoek (1632-1723), a tradesman of Delft, Holland was a contemporary and friend of the painter Johannes Vermeer. Vermeer, who painted some of the most luminous paintings ever seen, used an optical device (a camera obscura) to study light and perspective.
At some time before 1668 Leeuwenhoek started to construct microscopes used a single convex lens. In the end he made more than 500 “microscopes” with a basic design of one lens, mounted in a tiny hole in the brass plate that makes up the body of the instrument. The specimen was mounted on a sharp point that was in front of the lens, and its position and focus could be adjusted by turning the two screws. The entire instrument was only 3-4 inches long, and had to be held up close to the eye; it required good lighting and great patience to use. With this device he could obtain magnifications of 220 greater than normal size.
Leeuwenhoek described his observations with his microscope in letters he sent to the Royal Society of London, which were then published in the Philosophical Transactions of the Royal Society of London.
In 1686 he sent the Royal Society a letter on the capillary circulation. When he directed his microscope to the tail of the tadpole:
"A sight presented itself more delightful than any mine eyes had ever beheld; for here I discovered more than fifty circulations of the blood in different places, while the animal lay quiet in the water, and I could bring it before my microscope to my wish. For I saw not only that in many places the blood was conveyed through exceedingly minute vessels, from the middle of the tail toward the edges, but that each of the vessels had a curve or turning, and carried the blood back toward the middle of the tail, in order to be again conveyed to the heart. Hereby it plainly appeared to me that the blood-vessels which I now saw in the animal, and which bear the names of arteries and veins are, in fact, one and the same; that is to say, that they are properly termed arteries so long as they convey the blood to the furtherest extremities of its vessels, and veins when they bring it back to the heart. And thus it appears that an artery and a vein are one and the same vessel prolonged or extended.…the passing of the blood from the arteries into the veins, in the tadpoles, only takes place in such blood-vessels as are so thin that only one corpuscle can be driven through at one time…”
In 1674 Leeuwenhoek examined red blood cells, which had been discovered earlier by his fellow Dutchman, Jan Swammerdam. With his superior lens, Leeuwenhoek was able to give a clearer description of the cells than ever before and was the first person to accurately determine their size.
In 1676 Leeuwenhoek discovered bacteria in water, and in 1683 he discovered the lymphatic capillaries. His other discoveries were the branched character of heart muscles, the stripe in voluntary muscles, the structure of the crystalline lens and the description of spermatozoa.
"To see a World in a Grain of Sand
And a Heaven in a Wild Flower
Hold Infinity in the palm of your hand
And Eternity in an hour"
From: Auguries of Innocence, written in1803 by William Blake (1757 – 1827)
William Alocy. Biology and its Makers Third Edition 1908 New York Henry Holt
Hooke, Robert. (2009). Encyclopaedia Britannica. Encyclopaedia Britannica 2009 Deluxe Edition. Chicago: Encycloaedia Britannica.
Dorothy H ClarkeSource Book of Medical History 1960 Dover Edition (unabridged and unaltered) of 1942 edition Dover Publications New York
Laura J Snyder. Eye of the Beholder - Johannes Vermeer, Antoni van Leeuwenhoek and the Reinvention of Seeing. 2015 Head of Zeus, Clarendon House London