The counterpart to the great scientific genius that Copernicus was, the generalizer who discloses a new horizon, was to be found in his contemporary, Leonardo da Vinci, who was an inventor, a practical genius applying discoveries to everyday life. He solved most of the mechanical problems, invented locks for ca.n.a.ls, the wheelbarrow and special methods of excavation, a machine for making files by machinery, run by a weight, a machine for sawing marble blocks instead of separating them by natural cleavage, the model of those still employed at Carrara, as well as machines for planing iron, for making vices, saws and planes, for spinning, for shearing the nap of cloth, as well as an artist"s sketching stool, a color grinder, a spring to keep doors shut, a roasting jack, a hood for chimneys, movable derricks quite similar to those in use among us to-day, with contrivances for setting up marble columns on their bases, one of which in principle was used to set up Cleopatra"s Needle on the Embankment in London in our time. A favorite field of invention was that of all sorts of apparatus relating to war, military engines, devices for pushing scaling ladders away from walls and many others.
He was probably the greatest inventive genius in the world"s history.
He had an eminently practical mind. He devoted himself to the problem of flying, studied the wings of birds and produced a series of mechanical devices, tending toward the solution of that problem.
Taine said of him: "Leonardo da Vinci is the inventor by antic.i.p.ation of all the modern ideas and of all the modern curiosities, a universal and refined genius, a solitary and inappeasable investigator, pushing his divinations beyond his century so as at some times to reach ours."
There was scarcely anything that he touched that he did not illuminate wonderfully by his genius. In studying the muscles of animals he invented a {354} dynamometer, he improved spectacles and studied the laws of light, invented the camera obscura and in his steam experiments antic.i.p.ated Watt. A very curious feature of his work is his series of experiments with the steam gun, with which he was sure that great destruction might be worked.
A very interesting invention of a scientific instrument of some precision by Leonardo was what may be called a weather gauge. This was made of a copper ring with a small rod of wood, which acted as a balance. On it were two little b.a.l.l.s, one covered with wax and the other with material that absorbed moisture readily. When the air was saturated with moisture this ball grew heavy and inclined the beam till it touched one of the divisions marked on the copper ring set behind it. The degree of moisture could thus be seen and the weather, or at least changes in it, could be predicted. We have a whole series of such arrangements mainly in the shape of toys in the modern time.
The hygroscopic qualities of cord or the tendency of certain colors to change their tints when more moisture is present are used to indicate approaching changes in the weather. Leonardo seems to have been the first to make use of this practically and he deserves the credit of priority in the invention.
His studies in optics might almost naturally be expected from a painter so much occupied with color and whose intense curiosity prompted him to know not merely the use of things but the causes of and the reasons for them. He evolved much of the science of color vision, suggested the principles of optics that came to be known only much later, a.n.a.lyzed and explained the construction of the eye, invented the camera obscura in imitation of it and gave us a theory of color vision which is as good as any other that we have down to the present day. These optical studies alone might well be considered as enough to occupy an ordinary lifetime, but they seem to have been only the results of a series of interludes of the nature of recreation for Leonardo. He made his notes on the subject, filed them away with others, made no attempt to print his conclusions, probably found very few with whom he could discuss the subject, but he had satisfied himself. That was what he wanted.
{355}
After knowing such facts as this we are not surprised to learn of his antic.i.p.ating by some sort of divination the laws of gravitation, the molecular composition of water, the motion of waves, the undulatory theory of light and heat, the earth"s rotation and rotundity before Columbus" time and many other surprising things. One finds in his diary that he was planning the construction of a harbor and studying the music of the waves on the beach at the same time.
Poggendorff, in his great Biographical Dictionary of prominent men of science, quotes Libri"s "History of Mathematics in Italy" as authority for the declaration that Leonardo discovered capillarity and diffraction, made use of the signs + and -, knew the camera obscura (without a lens), made observations on resistance, on density, on the weight of the air, on dust figures, on vibrating surfaces and on friction and its effects.
All sorts of machines came from Leonardo"s hands. He had a positive genius for practical invention that has probably never been equalled, surely not surpa.s.sed, even down to our own day. His inventive faculty worked itself out, in machines of such variety as have never come from the brain of a single individual before. Nor were these merely primitive mechanical devices that we would surely despise now. On the contrary, nearly all of them have endured in principle at least and some of them almost as they came from him.
Leonardo also did distinguished work in the biological sciences, so that Duval, Professor of Anatomy at the University of Paris and himself well known both for his researches in biology and his knowledge of the history of science, ent.i.tles an article with regard to him in the French _Revue Scientifique_ (Dec. 7, 1889), "A Biologist of the Fifteenth Century." His biological discoveries are discussed in the chapter on the Biological Sciences.
Sometimes it is a.s.serted by those who are so little familiar with the history of science that they venture on such a.s.sertions rather easily, that the true scientific spirit had not yet awakened and that while men were making many observations and acquiring new information they had not as yet the proper scientific att.i.tude of mind to make really great discoveries. It is {356} rather amusing to be told that of a century when Copernicus and Vesalius and so many other distinguished modern scientists were alive. Some writers suggest that the true rising of the modern spirit of scientific inquiry did not come until Francis Bacon"s time. Francis Bacon is one of the idols of the marketplace, but surely no serious student of history accords him the place in science that our English forbears gave him when they were insular enough to know very little about continental work, and above all about Italian workers.
Francis Bacon, of course, had been long antic.i.p.ated in all that concerns the inductive method in science by his much greater namesake Roger Bacon. In Columbus" Century however, a hundred years before Bacon"s time, Bernardino Telesio, the Italian philosopher, stated fully the inductive method and recognized all its possibilities. In _Science_ for December 19, 1913, Professor Carmichael said of him:
"He abandoned completely the purely intellectual sphere of the ancient Greeks and other thinkers prior to his time and proposed an inquiry into the data given by the senses. He held that from these data all true knowledge really comes. The work of Telesio, therefore, marks the fundamental revolution in scientific thought by which we pa.s.s over from the ancient to the modern methods. He was successful in showing that from Aristotle the appeal lay to nature, and he made possible the day when men would no longer treat the _ipse dixit_ of the Stagirite philosopher as the final authority in matters of science."
The tendency of this century to make scientific principles of value for practical purposes is well ill.u.s.trated by the references to the sympathetic telegraph which began to be much talked of at this time.
According to the story as told, friends at a distance might be able to communicate with each other by having two dials around which the letters of the alphabet were arranged with a magnetic needle swinging free as the indicator. When the needle on one of the dials was moved to a letter, the other by magnetic attraction was supposed to turn to the same letter. This ingenious conceit has been attributed to Cardinal Bembo, one of the great scholars of the Renaissance, who was private secretary to Pope Leo X. His friend {357} Porta, the versatile philosopher, made it widely known by the vivid description which he gave of it in his celebrated work on "Natural Magic," published just after the close of Columbus" Century.
A very important development in science came in the application of chemistry to medicine, both as regards physiology and pathology. Basil Valentine at the beginning of Columbus" Century led the way and Paracelsus did much to indicate what the advantage of the application of chemistry to medicine would be. Paracelsus compared the processes in the human body with chemical phenomena and declared that alterations in the chemical conditions of organs were the causes of disease. He set himself up in opposition to the humoral theory of the ancients and denied that the heart was the seat of heat manufacture in the body, for every portion of the system had, he a.s.serted, its source of heat. It was through Paracelsus that chemistry was added to the medical curriculum and George Korn in his chapter on Medical Chemistry in Puschmann"s "Handbook" attributes the foundation of certain professorships for chemistry at the universities of this time to Paracelsus" influence. Andreas Libavius did much to advance chemical science in various directions by his study and preparation of sulphuric acid and his recognition of the ident.i.ty of the substance made from sulphur and saltpeter with that obtained from vitriol and alum. Studies of this kind brought a broad realization of the possibilities of chemistry.
The spirit of the period as regards science and the development of the faculty of observation at this time is very well ill.u.s.trated by Columbus" own observations on the declination of the magnetic needle during his first voyage across the ocean. Brother Potamian has told the story in "Makers of Electricity" (Fordham University Press, New York, 1909), page 22:
"It is one of the gems in the crown of Columbus, that he observed, measured and recorded this strange behavior of the magnetic needle in his narrative of the voyage. True, he did not notice it until he was far out on the trackless ocean. A week had elapsed since he left the lordly Teneriffe, and a few days since the mountainous outline of Gomera had disappeared {358} from sight. The memorable night was that of September 13th, 1492. There was no mistaking it; the needle of the Santa Maria pointed a little west of north instead of due north. Some days later on September 17th, the pilots, having taken the sun"s amplitude, reported that the variation had reached a whole point of the compa.s.s, the alarming amount of 11 degrees.
"The surprise and anxiety which Columbus manifested on those occasions may be taken as indications that the phenomenon was new to him. As a matter of fact, however, his needles were not true even at the outset of the voyage from the port of Palos, where, though no one was aware of it, they pointed about 3 east of north. This angle diminished from day to day as the Admiral kept the prow of his caravel directed to the West, until it vanished altogether, after which the needles veered to the West, and kept moving westward for a time as the flagship proceeded on her voyage.
"Columbus thus determined a place on the Atlantic in which the magnetic meridian coincided with the geographical and in which the needle stood true to the pole. Six years later, in 1498, Sebastian Cabot found another place on the same ocean, a little further north, in which the compa.s.s lay exactly in the north-and-south line. These two observations, one by Columbus and the other by Cabot, sufficed to determine the position of the agonic line, or line of no variation, for that locality and epoch.
"The _Columbian_ line acquired at once considerable importance in the geographical and the political world, because of the proposal that was made to discard the Island of Ferro and take it for the prime meridian from which longitude would be reckoned east and west, and also because it was selected by Pope Alexander VI to serve as a line of reference in settling the rival claims of the kingdoms of Portugal and Castile with regard to their respective discoveries. It was decided that all recently discovered lands lying to the east of that line should belong to Portugal; and those of the west to Castile."
The first observation of magnetic declination on land appears to have been made about the year 1510 by {359} George Hartmann, Vicar of the Church of St. Sebald, Nuremberg, who found it to be 6 East in Rome, where he was living at the time. He observed it also in Nuremberg, where the needle pointed ten degrees East of North. Columbus"
explanation of the declination to his sailors is interesting. He kept silence about it at first, but when they grew alarmed, believing that the laws of nature were changing as they advanced farther and farther into the unknown, he told them that the needle did not point to the North Star, which had been called the Cynosure, but to a fixed point in the celestial sphere and that Polaris itself was not stationary, but had a rotational movement of its own, like all other heavenly bodies. They trusted him and their fears were allayed and a mutiny averted. When on his return to Spain he reported the many and definite observations on the variation of the compa.s.s which he had made he was told by the scientists of the time that he, and not the needle, was in error, because the latter was everywhere true to the pole. Just why they were sure it was so they could not tell, but they refused to believe even observations which showed that it was not so; though these were reported by a man who had just overturned quite as strong convictions by sailing westward and reaching land. It is such contradictions of what seem to be obviously first principles of science that in all ages have const.i.tuted great discoveries and required genius to make them.
{360}
CHAPTER XI
BIOLOGICAL SCIENCES
It is usually a.s.sumed that the biological sciences have developed in comparatively recent years and that above all nearly 500 years ago in the fifteenth century there could be no question of any developments that would be of any serious significance in the history of science.
The word biology itself is only about a hundred years old and very often it is a.s.sumed that human interest in departments of knowledge begins with the naming of them. A period, however, that saw such magnificent work in the physical sciences and especially such a revolution of thought by means of observation as came through Copernicus" theory, was not likely to neglect the biological sciences entirely. As a matter of fact, biology, taking the word in its broadest sense, made some magnificent strides at this time. Perhaps no period until our own witnessed such significant advances in every department of the biological sciences.
It is often said that the people of the Middle Ages had very little interest in the world around them. Indeed, surprise is often expressed that they should not have occupied themselves more with the wonderful book of nature lying so invitingly open before them and given themselves more to nature study. Some have even ventured to seek the reason and have thought that they found in it an exaggeration of interest in another world than this, and mediaeval lack of interest in natural truth has been attributed to over-occupation with the supernatural. Those who dare to think, however, that the people of the Middle Ages were not interested in nature know nothing at all of the great writers of that time. They are profoundly ignorant of the broad interests of those whom they so lightly criticise. Dante is full of nature study. More than any modern poet, with perhaps one or two exceptions, he has used his {361} knowledge of nature and of science to ill.u.s.trate his meaning in many pa.s.sages of his poetry. One needs but turn to the "Divine Comedy" almost anywhere to prove this. In his "Treatment of Nature in Dante." Professor Oscar Kuhns of Wesleyan University has demonstrated this beyond all doubt.
Three voluminous encyclopaedias of knowledge, including many of the wonderful facts of nature, were compiled in the thirteenth century.
Such men as Albertus Magnus, who has many volumes of scientific writing on natural subjects and who made collections and observations of all kinds, Roger Bacon, who has so many almost incredible antic.i.p.ations of modern knowledge, and Thomas Aquinas, who used the facts of nature as known in his time for the basis of his philosophy quite as Aristotle did long before, all were enthusiastic nature students. They did not know many things which the modern schoolboy can easily learn, for we have acc.u.mulated a great deal of information; since not a little that they thought they knew was wrong,--but that has been true in every period of the world"s history of science and even our own will not escape that inevitable law, but they knew ever so much more than is usually thought and what they knew was much more significant for real scientific progress than any but special students of their works have any idea of.
It will not be surprising, then, to find that there were magnificent foundations laid in the biological sciences in Columbus" Century, and that indeed the work of this period represents some of the most important fundamental truths in these sciences. Anatomy, for instance, received a development during the Renaissance period that made it an independent scientific department. Men began to think again for themselves and make their own observations in the first half of the century. It is rather interesting to see the details that were added to the previous knowledge of anatomy, for these demonstrate the fact that they were observing accurately; A few examples will suffice to make this clear.
Achillini noticed the _ductus choledochus_, the duct leading from the liver into the duodenum, and described the ilio-caecal valves.
Berengar of Carpi corrected a number of mistakes that had existed in Mondino"s _Anathomia_, the text-book {362} which had been most used since the beginning of the fourteenth century, and he discovered the foramina in the sphenoid bone. He will have, perhaps, still more of interest for our time, because he was the first to describe the vermiform appendix. He was also the first apparently to call attention to the fact that the thorax in men and the pelvis in women are wider in each case proportionately than in the other s.e.x, and that roughly, while the feminine form is conical, the masculine is an inverted cone.
Canani added much to the description of the muscles and was the first to notice the presence of valves in veins, discovering them in the _vena azygos_. Gabriele Zerbi noted the oblique and the circular muscles of the stomach and described the puncta lachrymalia, the ligamenta uteri and other anatomical details which had escaped description previously. His book on anatomy divided the bones and muscles and blood vessels into different chapters, and order was beginning to come out of the confusion that had existed because of the too-generalized teaching before.
It is of the anatomists of this time that Puschmann in his "History of Medical Education" says, "The Italian anatomists had the habit of making the dissections of bodies for themselves, and it is for this reason that all the great anatomical discoveries of the time come from Italy. The anatomical schools of that country were the best in the world. All the greatest anatomists of the sixteenth century received their education there, and among the masters of the Italian schools are to be found the greatest names of which the science of anatomy can boast." Neuberger in his "Handbook of the History of Medicine"
[Footnote 30] says, "The Italian professors, incited by the brilliant example of "Mondino," surpa.s.sed all the other anatomists of the world because they did not disdain to take in their own hands the anatomical scalpel, and it is for that reason that at this time anatomy in Italy was cultivated with greater breadth of vision than elsewhere. The Italian anatomists initiated at the end of the fifteenth century the most famous period in the history of the art of dissection {363} and became the teachers to the physicians of the whole world."
[Footnote 30: Neuberger u. Pagel: _"Handbuch der Geschichte der Medicin";_ Jena, 1903, Vol. II, p. 23.]
Martinotti in his "The Teaching of Anatomy in Bologna Before the Nineteenth Century" [Footnote 31] gives a very good idea of the thoroughly scientific spirit of their investigations and their ardent curiosity with regard to anatomical details, as these may be gathered from the commentaries of Berengar of Carpi. He says, for instance, "Let no one think that by word of mouth alone or the study of books, this science of anatomy" [he calls it discipline] "can be learned. For this the sight and touch are absolutely necessary." "Nor can any real knowledge of the members of the human body be obtained from a single dissection, for this a number of dissections are required." He himself says in suggesting with true scholarly spirit how little he knows in spite of his opportunities, in order that others may be encouraged to take as many opportunities as possible, "how many hundreds of cadavers have I not dissected." This expression is sometimes said to be an exaggeration, but it is in accord with the whole trend of Berengar"s method of study. A dissection in the old time did not mean a complete study of the anatomy of the body by anatomical methods, but any opening of the body, in order to determine a particular point or to study any special part, was called an anatomy or dissection. Berengar insists frequently that a number of preparations and sections of the same viscus should be studied. He confesses that he had sectioned more than 100 cadavers in order to determine a question in brain anatomy and yet was not satisfied.
[Footnote 31: G. Martinotti: _L"Insegnamento dell" Anatomia in Bologna Prima del Secolo XIX;_ Bologna, 1911.]
The interests of the artists of the Renaissance in painting not merely the surface of things, but giving an idea of what they actually were, led to a great development of curiosity as to the const.i.tution of human beings. Not a single great artist of the Renaissance failed to make dissections for himself, and the greater the artist, the more dissections, as a rule, we know he made. Michelangelo dissected portions at least of more than 100 bodies, and Leonardo da Vinci probably did even much more than that. He proposed at one time to write a {364} textbook of anatomy. Ordinarily, it would be presumed that any such proposition from an artist could scarcely be taken seriously in the sense of a scientific text-book to represent real contributions to anatomy as a science, though it might, of course, be valuable for artists. In recent years, however, the republication of the sketches of his dissections shows that Leonardo da Vinci might have written a very wonderful textbook of anatomy and that his plates are still valuable for the study of professed anatomists.
William Hunter declared that "Leonardo was the greatest anatomist of this period," and, as altogether we have some 750 separate sketches of dissections which he had actually studied, some idea of how much he accomplished can be obtained. These sketches represent not merely the muscles and the skeleton, though they give these very well and especially suggest their functions very completely, but they also contain sketches of all the viscera and even cross-sections of the brain at different planes. This book alone, without anything further, would give Leonardo a distinguished place in the history of physiology as well as of anatomy.
With all this in mind, it is amusing to know the impression rather prevalent among even educated people that there was Church opposition to dissection at this time, and to have such books as President White"s "Warfare of Science with Theology" represent Vesalius a generation after this as dissecting in fear and trembling because of the danger he was incurring from the violation of ecclesiastical laws against dissection. No such laws were ever in existence, and dissection for scientific and artistic purposes was apparently much better provided for than it is even in our time, and above all much better cared for by the ecclesiastical authorities who might have hampered it so much, than it was in the English-speaking countries two or three generations ago, when ardent students of anatomy had either to "resurrect" bodies themselves or buy them--as many of them did--from "resurrectionists," with all the abuses connected with this practice, in order to secure anatomical material.
The supreme development of anatomy in Columbus" Century came with Vesalius. After exhibiting his trend of mind {365} towards scientific and especially biological studies as a boy by the dissection of small animals, the suggestion for which had come to him from the study of Albertus Magnus" books, Vesalius went to Paris in order to find opportunities for anatomical study; but while profiting not a little there, he was rather disappointed because of the lack of facilities.
The jealousy of his teacher, Sylvius, which he aroused, made his work still more difficult, so he went down to Italy, where he knew that he could secure material for dissection and opportunities for study.
There, before he was twenty-five, they made him professor of anatomy at the University of Padua, and he had the opportunity to write his great text-book on anatomy, the _"De Fabrica Humani Corporis,"_ which has remained a cla.s.sic down to our day.
It would be rather difficult to enumerate all the discoveries that we owe to Vesalius. He well deserves the name of the Father of Modern Anatomy. Practically all of his productive life comes in Columbus"
Century, and he ill.u.s.trates how thorough the scientific men of the time were in their modes of thinking and ways of observation. Details that might have been expected to escape him are described most clearly. He was the first to point out that nerves penetrated muscles and to suggest the physiological function that they performed of bringing about contraction. He discovered the little blood vessels that enter bones, the nutrient arteries, but still more definitely described the nutrition of bones through the periosteum and its rich blood supply. He added greatly to the knowledge of the time as regards the anatomy of the abdominal wall and of the large organs of the abdominal cavity, especially the stomach and the liver. His descriptions of the s.e.x organs are far in advance of all that his predecessors had known, and here his anatomical knowledge also became of value for suggestions in physiology,--the two cognate sciences were, as might be expected, developing together. Vesalius described the heart completely and suggested its mechanism, and yet could not get away from Galen"s declaration that the blood pa.s.ses through the septum of the heart. His description of blood vessels and their inner and outer coat shows how carefully his observations were made. He declared {366} afterwards that he was led to make these investigations by the memory of his dissection of the bladders with which he used to play as a boy and which he found to consist of several coats.
There is scarcely a department of anatomy on which Vesalius" name is not stamped deeply. He devoted great care, for instance, to the examination of the brain, emphasized the distinction between the gray and white matter, described the corpus callosum, the septum lucidum, the pineal gland and the corpora quadrigemina.
Two at least of Vesalius" disciples and a.s.sistants in teaching deserve to be named in the great development of anatomy that came at this time. One of them is Realdus Columbus, to whom we owe the discovery of the circulation of the blood in the lungs, and the other, Fallopius, whose name is familiar from its attachment to important structures in the body which he first described. Columbus we shall have more to say of under physiology, for the circulation of the blood was an important contribution to that science. Columbus" work was done at Rome, whither he was invited by the Popes to teach at the Papal Medical School, and where his directions and demonstrations were attended by cardinals, archbishops, and distinguished ecclesiastics. He had been Vesalius"
prosector at Padua and had succeeded him at Bologna, and then was invited to Rome. He wrote a great text-book of anatomy, which was dedicated to Pope Paul IV, and it was one of the treasures of the Renaissance both because of the development of anatomy which it represents, and its value as one of the early beautifully printed and ill.u.s.trated books of the medicine of this time.
Fallopius, the gifted pupil of Vesalius, of whom Haeser, the modern historian of medicine, has said that he was "one of the most important of the many-sided physicians of the sixteenth century," followed his master"s work, corrected some details of it and added many new facts.
We are not quite sure of the time of his birth, but he was probably less than thirty, perhaps only twenty-five, when he became professor of anatomy at Ferrara. He subsequently occupied the chair of anatomy at Pisa, and later of anatomy and surgery at Padua. He {367} added much to what was known before about the internal ear and described in detail the tympanum and its relations to the osseous ring in which it is situated. He also described minutely the circular and oval windows and their communication with the vestibule and cochlea. He was the first to point out the connection between the mastoid cells and the middle ear. His description of the lachrymal pa.s.sages in the eye was a marked advance on those of his predecessors, and he also gave a detailed account of the ethmoid bone and its cells in the nose. His contributions to the anatomy of the bones and muscles were very valuable. It was in myology particularly that he corrected Vesalius.
He studied the organs of generation in both s.e.xes, and his description of the ca.n.a.l or tube which leads from the ovary to the uterus attached his name to the structure. Another discovery, the little ca.n.a.l through which the facial nerve pa.s.ses after leaving the auditory, is also called after him the _aquaeductus Fallopii._