|HISTORY OF MEDICINE
|Year : 2003 | Volume
| Issue : 1 | Page : 8
"The Eternal Thing in Man"
"Director, Non-Invasive Cardiac Laboratory, Cardiology & Cardiovascular Surgery Department, Hamad Medical Corporation, Doha, Qatar
|Date of Web Publication||22-Jun-2010|
Director, Non-Invasive Cardiac Laboratory, Cardiology & Cardiovascular Surgery Department, Hamad Medical Corporation, Doha
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Hajar R. "The Eternal Thing in Man". Heart Views 2003;4:8
I am the family face; Flesh perishes, I live on, Projecting trait and trace Through time to times anon, And leaping from place to place Over oblivion. The years-heired feature that can In curve and voice and eye Despise the human span Of durance - that is I; The eternal thing in man, That heeds no call to die.
[Additional file 1]
"The eternal thing in man" was not given a name until 1869 when a Swiss chemist, Johann Friedrich Miescher, identified 'nuclein', a white, powdery substance within cells that was later called nucleic acid. Meischer surmised nucleic acid could be the "key" to the inheritance code  . Subsequently, nucleic acid was isolated, purified, and given the name deoxyribose nucleic acid or DNA. Sixty years after Meischer's discovery, Oswald Avery proved that DNA was indeed responsible for inheritance  . Thus, the race among scientists to discover its structure began, culminating in April 25, 1953 with the historic publication by James Watson and Francis Crick describing the structure of DNA in the journal Nature  . Watson and Crick revealed to the world the now famed and elegant double helix structure, hinting that the two-stranded DNA allows it to create identical copies of itself. That was 50 years ago.
The DNA molecule has fascinated and enthralled scientists and lay people for half a century. The revelation of its structure laid the foundation for intense and exciting research in molecular biology, consequently elucidating various genetic molecular processes such as inheritance and replication of genetic material and molecular damage and repair. Watson and Crick, together with Maurice Wilkins, shared the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material"  .
| The Concept of Heredity in Antiquity|| |
It has long been recognized that heredity plays a significant role in determining not merely the characteristics of plants and animals but also the mental and physical qualities of human beings. Early humans from the Neolithic period must have had a glimmer of understanding that certain characteristics or traits are passed on from generation to generation. They probably learned, through observation, that they could improve the quality of their crops by selecting the hardiest, tastiest, and most productive breed. Ancient farmers in Mesopotamia (Iraq) selectively bred crops and animals that were most useful to mankind. Such selected breeding techniques permitted the transition from a nomadic to a sedentary and agriculture-based society.
Likewise, the resemblance or non-resemblance in appearance and behavior between members of the same family, clan, tribe, or race was noted in ancient times. They must have speculated on an explanation for such phenomena, forming a kind of primitive theory based on "blood-line."
In virtually all early societies and civilizations, the social group was perceived by its members as an intergenerational affair, with the family and its ancestors playing an important role in the self-concept of the individual. Life does not begin, nor does it end, with the individual. The individual was perceived as a living link in the chain that was the lineage. Each clan or tribe had its own distinctive "blood-line" - what modern science refers to as "gene pool." Reproduction was considered a sacred duty, to perpetuate the individual's ancestry.
By the time civilizations flourished along the rivers Tigris and Euphrates and the river Nile, it was recognized that heredity played an important role in determining the character and abilities of men and women. Kings and heroes were believed to inherit qualities superior to those of the average man, and to carry these qualities in their "blood." From whence or from whom did the superior qualities originate? From the gods, obviously, since they were perceived as powerful and superior beings. The kings of antiquity shrewdly recognized and understood the psychological impact of pedigree and hence, they traced descent from the immortal and powerful gods to highlight their supremacy and legitimize their right to rule. Kingship was hereditary. Ancient eastern and western mythology is full of stories of kings and heroes descended from the gods and endowed with superhuman qualities, performing great deeds.
In ancient Greece, the belief that character and bearing were inherited from ancestors was widespread. Thus, in Homer's Odyssey, King Menelaus, greets two strangers visiting his house: "Welcome . . . I shall ask who you are, for the blood of your parents was not lost in you, but ye are of the line of men that are sceptered kings, the fosterlings of Zeus, for no churl could beget sons like you"  . Pedigree was flaunted to impress and gain a psychological advantage, especially in battle, imparting an air of prowess and invincibility to its possessor. Thus, in Homer's Iliad, we find warrior-heroes frequently boasting of the nobility of their lineage and descent to their enemy before engaging in fierce combat:
"Son of Peleus, think not that your words can scare me . . . We know one another's race and parentage as matters of common fame . . ." 
"Who and whence are you who dare to face me? . . . I am of the seed of mighty Zeus . . . mightier than any god . . . so are his children stronger . . . 
Homer, The Iliad
In Homeric Greece, truthfulness was an admired quality and it was deemed an inherited virtue. Greek literature and proverbs are replete with passages underlining the belief that personal features and character were inherited: "Noble children are born from noble sires, the base are like in nature their father" (Alcmeaon, Fr. 7); "I bid all mortals beget well-born children from noble sires" (Heraclitus, 7); "If one were to yoke good with bad, no good offspring would be born, but if both parents are good, they will bear noble children" (Meleager, Fr.9).
Ancient Greek scientists and physicians pondered heredity. According to Hippocrates (c. 460-377 BC), inherited qualities, in some way or other, must have been transmitted to the offspring from different parts of the organisms of the father and the mother. Tiny particles of every part of each parent fused together during the act of reproduction to create an offspring that was an amalgamation of the two. This was called "pangenesis"  . Hippocrates stated, "bald people are descended from bald people, people with blue eyes from people with blue eyes, and squinting persons from squinting persons", but qualified it by adding, "in the majority of cases."
Hippocrates went beyond the inheritance of physical appearance by linking human behavior to four bodily fluids or "humors." He classified personalities into four types related to the four humors: Choleric or hot-tempered people had yellow bile; confident individuals were sanguine (blood); melancholic/moody people had black bile; and those slow to take action were phlegmatic. Aristotle (c.384-322BC), however, distinguished between pedigree and character: "Being well-born, which means coming of a fine stock, must be distinguished from nobility, which means being true to the family nature . . .  .
Long before Mendel, Aristotle alluded to the appearance and disappearance of traits: "In the generations of men, as in the fruits of the earth, there is a varying yield; now and then, where the stock is good, exceptional men are produced for a while and then decadence sets in"  .
It was commonplace and accepted theory that parental characteristics were passed on to succeeding generations through "blood line", but just how this was accomplished remained a mystery for thousands of years - that is, until 50 years ago.
| Unraveling the 'secret of life'|| |
"We have found the secret of life", boasted Francis Crick at a pub in Cambridge, England on February 28, 1953  . Indeed, Crick and his co-researcher James Watson had, THAT MORNING, figured out the structure of deoxyribonucleic acid - DNA - the key to life.
Watson and Crick published their discovery in April 1953, in the journal Nature, unveiling a "double helix" structure. They flipped a coin to settle the question of byline: Watson and Crick, or Crick and Watson? Their paper stated with great reserve and restraint: "It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material"  .Their statement has been dubbed "one of the most famous understatements in the history of science", for their discovery gave us the key to understanding how life perpetuates itself.
Both Crick and Watson were influenced by a little book called What Is Life? that appeared in 1944, by Erwin Schrodinger, an Austrian physicist. Schrodinger argued that life could be thought of in terms of storing and passing on biological information. Chromosomes were thus simply information bearers. Because so much information had to be packed into every cell, it must be compressed into what Schrodinger called a "hereditary code-script" embedded in the molecular fabric of chromosomes. To understand life then, these molecules had to be identified and their code deciphered  . It appears that Schrodinger's little book fired the imagination of many scientists at that time, setting them off on the quest to unravel the "secret of life."
In 1951, Crick and Watson formed a close working relationship, and collaborated to discover the structure of the molecule DNA. They were convinced that if the three-dimensional structure of a molecule known to play a role in passing genetic information - DNA - could be determined, then the way genes are passed on might also be revealed. They made models based on research done in several fields. They were getting closer, as were other scientists chasing the same goal; a race was heating up. Rosalind Franklin, a physical chemist researcher at King's College in London, was also working on the DNA project, on x-ray diffraction data of DNA. She and her co-investigator, Maurice Wilkins, did not get along and were not even on speaking terms. Franklin had taken the image of the x-ray diffraction pattern from crystalline DNA showing a clear cross shape [Figure 1]. According to Watson, this estrangement led Wilkins to show Watson the cross shape image, which had not yet been published  . The sneak preview enabled Watson and Crick to put the final piece in the puzzle. In 1953, they created a visual model of DNA, which later proved to fit all experimental evidence.
Watson, Crick, and Wilkins shared a Nobel Prize for their work in 1962, but Franklin had died of ovarian cancer in 1958 at the age of 37. Nobel Prize rules do not allow for posthumous awards. In Crick's view, if Franklin had lived, "she would have shared the prize because she did the key experimental work."
| The double helix DNA - The gene|| |
"Almost all aspects of life are engineered at the molecular level, and without understanding molecules, we can only have a very sketchy understanding of life The three-dimensional molecular structure of DNA - the double helix - is built like a double spiraling ribbon or strand or chain [Figure 2]. The two chains are held together by strong hydrogen bonds between adenine-thymine and guanine-cytosine base pairs. If the sequence or order of the bases along one chain is known, the sequence along the other can be inferred. Genetic messages in genes are copied exactly when chromosomes duplicate prior to cell division - the molecule unzips to form two separate strands. Each separate strand serves as the template for the synthesis of a new strand, and so, one double helix becomes two  . That, in a nutshell, is how traits are passed on from parent to offspring.
DNA is the molecule of heredity - the gene, which is made up of four chemical chains in a special sequence: Adenine (A) bonds with thymine (T); cytosine(C) bonds with guanine (G) .
These four letters form the "code of life", which is carried in the gene. The code is the instruction - the template - for making proteins, the building blocks of life.
| Before the double helix: Darwin and Mendel|| |
"Descended from the apes? My dear let us hope that is not true, but if it is, then let us pray that it will not become generally known," said the wife of the bishop of Worcester after she had learned about The Origin of Species by Charles Darwin  . However, scientists such as Thomas Huxley hailed the book, and Huxley is quoted as having exclaimed, "How extremely stupid not to have thought of that!"
Darwin's book, first published in 1869, was revolutionary. It was sensational, and although the general public considered it scandalous, it sold out on the first day of publication. God, however, did not grant the hope of the bishop's wife that the information remains hidden. Darwin's theory of evolution by natural selection continues to stir passionate debate or denial among lay people to this day. In Darwin's view, members of a population vary in heritable traits. Variations that improve chances of surviving and reproducing show up more often in each generation. Characteristics that do not improve survival become less frequent. In time, the population changes - it evolves  .
However, Darwin could not explain how various characteristics were inherited from generation to generation. He wrote: ". . . no-one can say why the same peculiarity in different individuals . . . is sometimes inherited and sometimes not so: why the child often reverts in certain characters to its grandfather, or other much more remote ancestor; why a peculiarity is often transmitted from one sex to both sexes, or to one sex alone, more commonly but not exclusively to the like sex"  . That piece of the puzzle was filled in by Gregor Mendel (1822-1884), an eccentric and scholarly Austrian monk. Trained in physics and recruited to a monastery in Europe to do research into breeding plants and animals, Mendel used observation and scientific principles in his work. Mendel was not the first to notice that the characteristics of animals and plants are passed down through each generation, but he was the first to use statistics with his genetic results. By performing breeding experiments with the sweet pea plant, he gradually saw there were certain patterns in the baby plants. These patterns, such as the ratio of red flowers to white flowers always being 1 to 3, suggested there was a basic law of heredity that was being obeyed  .
In the process of experimenting, Mendel reportedly counted approximately 28,000 pea plant seeds over a period of seven years. He studied easily distinguishable characteristics like the color and texture of the peas, smooth or wrinkled seeds, the color of the pea plants and flowers, and the height of the plants. Mendel did his work with ordinary garden peas in an ordinary small garden next to his monastery. He took the male pollen from the flowers of tall-stemmed pea plants and with it, carefully pollinated the flowers from short-stemmed pea plants. When he grew all the seeds that these cross-pollinated flowers produced, all the pea plants were tall  . (One can imagine Mendel muttering to himself, "Gee, that's funny . . . where are the short ones?"). If short stems were an inherited trait, what had happened to this trait in the first generation of offspring? Mendel carried the experiment one step further. He crossed his first generation offspring with each other and he got pea plants of which three-fourths had tall stems and one-fourth had short stems  . The short-stem trait had not been lost; it had been the there all the time, but had been "hidden." In the next generation, though, it could reappear. And it did - in mathematically predictable ratios.
Mendel found that certain characteristics reappeared in fairly precise ratios; the ones that occurred most often he called dominant and the masked trait he called recessive. When he crossed true-breeding lines with each other, he noticed that the characteristics of the offspring consistently showed a 3 to 1 ratio in the second generation. The traits from each parent do not blend: they are inherited from the parents as "discrete units" and remain distinct  .
Mendel believed that these characteristics were passed on from plant to plant as "particles", of which each plant had two, one from each parent. To explain these patterns of heredity, Mendel proposed that parent plants always had two "factors", but that only one "factor" from each parent was passed on to each offspring  . Today, Mendel's "factors" are known as genes.
In 1866, Mendel described his experiments with peas, concluding that heredity was transmitted in "discrete units." The scientific community largely ignored Mendel's work. A few months before his death, Mendel is alleged to have commented, with a hint of resignation mingled with the awareness of the importance of his discoveries: "My scientific studies have afforded me great gratification; and I am convinced that it will not be long before the whole world acknowledges the results of my work"  . That prophesy came true 40 years after his death, when three botanists working independently on plant hybrids "rediscovered" Mendel. They were startled to find Mendel's old papers spelling out those laws in detail. Recognizing the importance of Mendel's seminal work, they acknowledged his legacy and hailed him as the Father of Genetics  .
By 1900, cells and chromosomes were sufficiently understood to give Mendel's abstract ideas a physical context. In 1909, the Danish botanist Wilhelm Johannsen coined the word "gene" to describe the Mendelian units of heredity. Gene is derived from the Greek word genos, meaning, "birth." The word also spawned others, like genome  .
The concepts that Mendel established in 1865 came to be known universally as Mendel's laws of heredity. He had discovered some near-universal rules governing inheritance. His insights still have the power to explain many of the puzzling and sometimes devastating aspects of inheritance that occupy our attention today.
| After the double helix: the human genome|| |
"Is there something divine at the heart of a cell that brings it to life? The double helix answered that question with a definitive No," stated Watson in his book, DNA: The Secret of Life  . The double helix shattered the long-held belief that there was something mystical in life's processes. It laid the foundation for understanding the essence of life - that life is a chemical process. This insight ushered in the era of genetic revolution.
Great and impressive advances have been accomplished since the double helix was first revealed. How the DNA code directs synthesis of proteins and how DNA mutations cause genetic diseases remained a puzzle until the 1960s. Proteins are not made directly from DNA. Instead, there is an intermediate called ribonucleic acid (RNA) that is a close chemical cousin of DNA. The DNA sequence is first encoded in an RNA sequence, and then the RNA sequence is used to actually make the protein. Hence, the flow of information proceeded from DNA to RNA to protein, with the DNA being left intact  . The isolation of genes and rapid reading of the genetic code was made possible with advances in DNA analysis methods such as genetic engineering, DNA sequencing, and DNA amplification. Finding faulty genes responsible for many diseases and mapping the genome of organisms became a reality.
In 1995, the genome of the bacterium Haemophilus influenza was completed. This exciting achievement was followed by the whole-genome sequencing of a nematode worm, C. elegans, in 1998. The sequencing of C. elegans was significant because it was the first complex animal to have its genome known. The fruit fly genome was completed in March 2000 and the mouse genome in December 2002  .
But by far the most ambitious undertaking has been the launch of the Human Genome Project in 1990. The project passed a thrilling milestone when the "rough draft" of the human genome was published in June 2000. It was initially estimated that the human genome contained 70,000 to 150,000 genes but the most recent analysis puts the value much lower: 30,000 to 40,000  .
On April 14, 2003, The International Human Genome Sequencing Consortium announced the successful completion of the Human Genome Project. It has been sequenced to an accuracy of 99.99 percent.
"Never would I have dreamed in 1953 that my scientific life would encompass the path from DNA's double helix to the 3 billion steps of the human genome . . . The completion of the Human Genome Project is a truly momentous occasion for every human being around the globe", said James Watson, Nobel Laureat, and first director of the Human Genome Project  .
| Medicine after the human genome|| |
The completion of the human genome is a truly historic event, and no doubt it will revolutionize the future practice of medicine. Since 1996, when the Human Genome Sequencing Consortium adopted the so-called "Bermuda Principles", which expressly call for automatic, rapid release of DNA or gene discoveries to the public domain, more than 1,400 disease genes have been identified, in contrast to the fewer than 100 human disease genes known in 1990 at the start of the Human Genome Project  .
The completed human genome is a great foundation upon which to build the science and medicine of the 21st century. It is the beginning of a "new medicine." Undoubtedly, the human genome will lead to better understanding of diseases. Hopefully, new tools will be developed to allow assessment of the hereditary contributions to common diseases such as diabetes, hypertension, and heart disease. Anticipated benefits include the early detection and improved diagnosis of disease (genetic testing), early detection of genetic susceptibility to disease, more personalized drug prescription (pharmaco-genetics), development of new drugs to more specifically target the root cause of disease, and gene therapy.
At the present time, gene therapy is still experimental but it holds potential for treating or even curing genetic and acquired diseases such as cancers and infections by using normal genes to supplement or replace defective genes or to bolster a normal function such as immunity  . More than 600 clinical gene-therapy trials involving about 3500 patients were identified worldwide in 2002  . Although most trials focus on various types of cancer, studies also involve other diseases with multigenic and monogenic causes, infectious diseases, and vascular diseases. Most current protocols are aimed at establishing the safety of gene-delivery procedures rather than effectiveness  . Gene transfer still faces many obstacles before it can become a practical approach for treating disease.
One of the most controversial aspects of genomics is genetic engineering or germline engineering, which is the editing of DNA inheritance passed down from one generation to the next. The Human Genome Organization's (HUGO) Ethics Committee called for a clear distinction between therapy for medical disorders, and enhancement, i.e., use of the same techniques to alter heritable traits. The HUGO Ethics Committee issued a statement in 2001 that although human gene therapy is still risky, the trials should go on; but human genetic enhancement was unacceptable  . However, the new genome information could make various forms of genetic engineering faster and easier. The technique of identifying an abnormal gene and then correcting that gene in eggs and sperm would mean that no further generations would be affected by any genetic defects from their ancestors  . Such interference is still hotly debated.
The sequencing of the complete human genome has ushered in the epoch of DNA-based medicine. Medical genetics is no longer an exotic specialty for the diagnosis of rare inherited diseases. Its influence and potential uses extend to all aspects of medical care. The individual patient's genome will help determine the optimal approach to patient care whether it is preventive, diagnostic, or therapeutic. To keep pace with this transformation in clinical practice, it is imperative that we learn and understand the concept of genetic variability, its interactions with the environment, and its implications for patient care. We also must familiarize ourselves with the various ethical and legal implications of gene-based medicine.
| Our identity: who we are|| |
"Now we know, in large measure, our fate is in our genes", so said James Watson  . At the heart of philosophical and scientific debates since ancient times is the question, who are we? Our sense of identity-ourselves-is closely bound up with our perceived abilities (specifically our IQ), our preferences, and our emotions.
The explosion of genetic research in recent years has spawned the idea that our genes make us who we are. From time to time, news of discovery of a particular gene controlling certain behavioral and emotional characteristics pop up in the lay press-"obesity gene", alcohol gene", "homosexuality gene", "bed-wetting gene", and "antisocial gene", among others. The list goes on. Such media reports give the impression that genes determine some of our most complex behaviors.
Are we merely puppets of our genes? While genetic research can determine the heritability of diseases, the genetic foundations of behavior are much more difficult to identify and quantify. The role of genetics (nature) and environment (nurture) in the creation of human personality is an age-old dispute.
In the 4th century BC, Aristotle concluded that the moral virtues or vices are shaped by both in-born predisposition (nature or heredity) and environment (nurture). On intelligence, to which Aristotle referred as "excellence of the reason", he was somewhat ambiguous on the role of environment, stating: "The excellence of the reason is a thing apart . . . it would seem also to need external equipment but little, or less than moral virtue does. Grant that both need the necessaries, and do so equally"  .
The controversy continues today. Some say environment plays the bigger part; others say genes do. Research into gene regulation and neurobiology has revealed intricate interactions among genes, proteins, hormones, food, and life experiences  . It is not unreasonable to conclude that both genes and environment play crucial roles in shaping our cognitive abilities and personalities.
| Conclusions|| |
The selective breeding of plants and animals is genetic manipulation and application of that masterful genetic insight 10,000 years ago, in Mesopotamia, changed the course of human history. Its impact on human progress and culture has been breathtaking. A secure and stable food supply allowed "free time" to invent writing, develop technology, science, and arts. It revolutionized human lifestyle and made possible the rise of civilizations. We are still reaping the benefits of that incredible achievement in the food we eat and enjoy: cereals, fruit, meat, and dairy products. It took us eons to reach the eve of another revolution - the DNA revolution, which was made possible with the unveiling of the structure of the DNA molecule, "the eternal thing." Completion of the Human Genome Project heralds yet another new era in human history, with far-reaching ramifications to society, including ethical and legal issues.
Medicine is at the crossroads. The potential benefit of genetics is tremendous. Understanding genes will have a profound effect on the practice of medicine. The ability to understand how genes and the other basic components of cells work together will illuminate people's hereditary risks and shed light on what goes wrong at the molecular level when diseases develop. Genetic factors that contribute to diseases will be better defined. Hopefully, insights will be gained on the complex and still poorly understood interplay of heredity and environment including diet and lifestyle in causing common diseases such as cancer, asthma, infections, diabetes, hypertension, and heart disease, to name but a few. Such knowledge will be useful for prediction of risk, risk stratification, prevention, and strategies for therapy.
The emergence of genetics as a powerful force in medicine and society has also raised new ethical and legal challenges; however, "the difficulty lies, not in the new ideas, but in escaping the old ones . . ."  .
| References|| |
|1.||A Dictionary of Scientists. New York, NY: Oxford University Press, 1999: Miescher, Johann Friedrich (1844 - 1895) Swiss biochemist. |
|2.||Landmarks in the history of genetics. http:// cogweb.ucla.edu/EP/DNA_history.html |
|3.||Watson J, Crick F. Molecular structure of nucleic acids. Nature. 1953; 171:736 - 737. |
|4.||The Nobel Prize in Physiology or Medicine 1962. http:// www.nobel.se/medicine/laureates/1962 |
|5.||Homer. The Odyssey. Book IV, 60. Translated by Samuel Butler http://classics.mit.edu/Homer/odyssey.html |
|6.||Homer.The Iliad. Translated by Samuel Butler http://classics.mit.edu/Homer/iliad.html |
|7.||Watson JD, Berry A. DNA: The secret of life. New York: Alfred Knopf, 2003. |
|8.||Aristotle. Nichomachean Ethics. Translated by W.D. Ross.http://www.theism.net/books/aristotle/ nicomachean.html |
|9.||Crick F. Of molecules and men. Seattle and London: Univesity of Washington Press, 1966. |
|10.||Darwin C. The origin of species. Complete and fully illustrated. Ed. Suriano G. New York: Gramercy Books; Random House, 1998. |
|11.||The history of modern genetics. http:// health.discovery.com/minisites/dn_zw_history.html |
|12.||Edelson E. Gregor Mendel and the roots of genetics. London: Oxford University Press, 2001. |
|13.||The human genome project. Step through time. Dynamic Timeline.http://www.genome.gov/Pages/Education/Kit/ main.cfm |
|14.||International Consortium completes Human Genome Project.http://www.ornl.gov/techResources/ Human_Genome/project/50yr/press4_2000.html |
|15.||Genomics and Its Impact on Science and Society: The Human Genome Project and Beyond. http:// www.ornl.gov/TechResources/Human_Genome/publicat/ primer2001/6.html |
|16.||Journal of gene Medicine. http://www.wiley.co.uk |
|17.||Pearson H. Human gene therapy worth the risk. Nature Science Update, 20 April 2001. http://www.nature.com/ nsu/010426/010426-3.html |
|18.||Jaroff L. The Gene Hunt. Time 1989, 20 March: 62-67. |
|19.||Berkowitz A. Our genes, ourselves? Bioscience 1996; 46(1): 42 - 51. |
|20.||Quote by John Maynerd Keynes as quoted in Drexler K. Eric Engines of Creation: the Coming Era of Nanotechnology, New York, Bantam, 1987:231. |
[Figure 1], [Figure 2]