As illustrating how, as we know more about the details of medical history, the beginnings of medical science and medical practice are pushed back farther and farther, a discussion in the Berliner klinische Wochenschrift a dozen years ago is of interest. Professor Ernest von Leyden, in sketching the history of the taking of the pulse as an important aid in diagnostics, said that John Floyer was usually referred to as the man who introduced the practice of determining the pulse rate by means of the watch. His work was done about the beginning of the eighteenth century. Professor von Leyden suggested, however, that William Harvey, the English physiologist, to whom is usually attributed the discovery of the circulation of the blood, had emphasized the value of the pulse in medical diagnosis, and also suggested the use of the watch in counting the pulse. Professor Carl Binz, of the University of Bonn, commenting on these remarks of Professor von Leyden, called attention to the fact that more than a century before the birth of either of these men, even the earlier, to whom the careful measurement of the pulse rate is thus attributed as a discovery, a distinguished German churehman, who died shortly after the middle of the fifteenth century, had suggested a method of accurate estimation of the pulse that deserves a place in medical history.
This suggestion is so much in accord with modern demands for greater accuracy in diagnosis that it seems not inappropriate to talk of it as the first definite attempt at laboratory methods in the department of medicine. The maker of the suggestion, curiously enough, was not a practising physician, but a mathematician and scholar, Cardinal Nicholas of Cusa, who is known in history as Cusanus from the Latin name of the town Cues on the Moselle River, some twenty-five miles south of Treves, where he was born. His family name, Nicholas Krebs, has been entirely lost sight of in the name derived from his native town, which is the only reason why most of the world knows anything about that town. Cardinal Cusanus suggested that in various forms of disease and at various times of life, as in childhood, boyhood, manhood, and old age, the pulse was very different. It would be extremely valuable to have some method of accurately estimating, measuring, and recording these differences for medical purposes. At that time watches had not yet been invented, and it would have been very difficult to have estimated the time by the clocks, for almost the only clocks in existence were those in the towers of the cathedrals and of the public buildings. The first watches, Nuremberg eggs, as they were called, were not made by Peter Henlein until well on into the next century. The only method of measuring time with any accuracy in private houses was the clepsydra or water-clock, which measured the time intervals by the flow of a definite amount of water. Cardinal Cusanus suggested then that the water-clock should be employed for estimating the pulse frequency. His idea was that the amount of water which flowed while a hundred heats of the pulse were counted, should be weighed, and this weight compared with that of the average weight of watcr which flowed while a hundred beats of the normal pulse of a number of individuals of the same age and constitution were being counted.
This was a very simple and a very ingenious suggestion. We have no means of knowing now whether it was adopted to any extent or not. It may seem rather surprising that a cardinal should have been the one to make such a suggestion. Cusanus, however, was very much interested in mathematics and in the natural sciences, and we have many wonderful suggestions from his pen. He was the first, for instance, to suggest., more than a century before Copernicus, that the earth was not the centre of the universe, and that it would not he absolutely- at rest or, as he said, devoid of all motion. His words are: ” Terra igitur, quae centrum esse nequit, motu omni carere non potent.” He described very clearly how the earth moved round its own axis, and then be added, what cannot fail to be a surprising declaration for those in the modern times who think such an idea of much later origin, that he considered that the earth itself cannot be fixed, but moves as do the other stars in the heavens. The expression is so astonishing at that time in the world’s history that it seems worth the while to give it in its original form, so that it may be seen clearly that it is not any subsequent far-fetched interpretation of his opinion, but the actual words themselves, that convey this idea. He said: ” Consideravi, quod terra ista non potest esse fira, sed movetur ut stellae.”
How clearly Cusanus anticipated another phase of our modern views may be judged from what he has to say in ” De Docta Ignorantia ” with regard to the constitution of the sun. It is all the more surprising that he should by some form of intuition reach such a conclusion, for the ordinary sources of information with regard to the sun would not suggest such an expression except to a genius, whose intuition outran by far the knowledge of his time. The Cardinal said: ” To a spectator on the surface of the sun the splendor which appears to us would be invisible, since it contain, as it were, an earth for its central mass, with a circumferential envelope of light and heat, and between the two an atmosphere of water and clouds and of ambient air.” After reading that bit of precious astronomical science announced nearly five centuries ago, it is easy to understand how Copernicus could have anticipated other phases of our knowledge, as he did in his declarations that the figure of the earth is not a sphere, but is somewhat irregular, and that the orbit of the earth is not circular.
Cusanus was an extremely practical man, and was constantly looking for and devising methods of applying practical principles of science to ordinary life. As we shall see in discussing his suggestion for the estimation of the pulse rate later on, lie made many other similar suggestions for diagnostic purposes in medicine, and set forth other applications of mathematics and mechanics to his generation.
Many of Cusanus’ books have curiously modern names. He wrote, for instance, a series of mathematical treatises, in Latin of course, on ” Geometric Transmutations,” on ” Arithmetical Complements,” on ” Mathematical Complements,” on ” Mathematical Perfection,” and on ” The Correction of the Calendar.” In his time the calendar was in error by more than nine days, and Cusanus was one of those who aroused sufficient. interest in the subject, so that in the next century the correction was actually madc by the great Jesuit mathematician, Father Clavius. Perhaps the work of Cusanus that is best known is that ” On Learned Ignorance-Docta Ignorantia,” in which the Cardinal points out how many things that educated people think they know are entirely wrong. It reminds one very much of Josh Billings’s remark that it is not so much the ignorance of mankind that makes them ridiculous, as the knowing so many things that ain’t so. It is from this work that the astronomical quotations which we have made are taken. The book that is of special interest to physicians is his dialogue ” On Static Experiments,” which be wrote in 1450, and which contains the following passages:
” Since the weight of the blood and the urine of a healthy and of a diseased man, of a young man and an old man, of a German and an African, is different for each individual, why would it not be a great benefit to the physician to have all of these various differences classified For I think that a physician would make a truer judgment from the weight of the urine viewed in connection with its color than he could make from its color alone, which might be fallacious. So, also, weight might be used as a means of identifying the roots, the stem, the leaves, the fruits, the seeds, and the juice of plants if the various weights of all the plants were properly noted, together with their variety, according to locality. In this way the physician would appreciate their nature better by means of their weight than if he judged them by their taste alone. He might know, then, from a comparison of the weights of the plants and their various parts when compared with the weight of the blood and the urine, how to make an application and a dosage of drugs from the concordances and differences of the medicaments, and even might be able to make an excellent prognosis in the same way. Thus, from static experiments, he would approach by a more precise knowledge to every kind of information.
” Do you not think if you would permit the water from the narrow opening of a clepsydra [water-clock] to flow into a basin for as long as was necessary to count the pulse a hundred times in a healthy young man, and then do the same thing for an ailing young man, that there would be a noticeable difference between the weights of the water that would flow during the period? From the weight of the water, therefore, one would arrive at a better knowledge of the differences in the pulse of the young and the old, the healthy and the unhealthy, and so, also, as to information with regard to various diseases, since there would be one weight and, therefore, one pulse in one disease, and another weight and another pulse in another disease. In this way a better judgment of the differences in the pulse could be obtained than from the touch of the vein, just as more can he known from the urine about its weight than from its color alone.
” Just in the same way would it not be possible to make a more accurate judgment with regard to the breathing, if the inspirations and expirations were studied according to the weight of the water that passed during a certain interval? If, while water was flowing from a clepsydra, one were to count a hundred expirations in a boy, and then in an old man, of course, there would not be the same amount of water at the end of the enumeration. Then this same thing might be done for other ages and states of the body. As a consequence, when the physician once knew what the weight of water that represented the number of expirations of a healthy boy or youth, and then of an individual of the same age ill of some infirmity or other, there is no doubt that, by this observation, he will come to a knowledge of the health or illness and something about the ease, and, perhaps, also with more certainty would be able to choose the remedy and the dose required. If he found in a healthy young man apparently the same weight as in an old and decrepit individual, he might readily be brought to the conclusion that the young man would surely die, and in this way have some evidence for his prognosis in the case. Besides, if in fevers, in the same way, careful studies were made of the differences in the weight of water for pulse and respiration in the warm and the cold paroxysms, would it not be possible thus to know the disease better and, per-bap, also get a more efficacious remedy? ”
As will be seen from this passage, Cusanus had many more ideas than merely the accurate estimation of the pulse frequency when he suggested the use of the water-clock. Evidently the thought had come to him that the specific gravity of the substances, that is, their weight in comparison to the weight of water, might be valuable information.
Before his time, physicians had depended only on the color and the taste of the urine for diagnostic purposes. He proposed that they should weigh it, and even suggested that they should weigh, also, the blood, I suppose in case of venesection, for comparison’s sake. lie also thought that the comparative weight of various roots, sterns, leaves, juices of plants might give hints for the therapeutic uses of these substances. This is the sort of idea that we are apt to think of as typically modern. Specific gravities and atomic weights have been more than once supposed to represent laws in therapeutics, which so far, however, we have not succeeded in finding, but it is interesting to realize that it is nearly five hundred years since the first thought in this line was clearly expressed by a distinguished thinker and scientific writer.
There are many interesting expressions in Cusanus’ writings which contradict most of the impressions commonly entertained with regard to the scholars of the Middle Ages. It is usually assumed that they did not think seriously, but speculatively, that they feared to think for themselves, neglected the study of nature around them, considered authority the important source of knowledge, and were as far as possible from the standpoint of modern scientific students and investigators. Here is a passage from Nicholas, on knowing and thinking, that might well have been written by a great intellectual man at any time in the world’s history, and that could only emanate from a profound scholar at any time.
” To know and to think, to see the truth with the eye of the mind, is always a joy. The older a mall grows the greater is the pleasure which it affords him, and the more he devotes himself to the search after truth, the stronger grows his desire of possessing it. As love is the life of the heart, so is the endeavor after knowledge and truth the life of the mind. In the midst of the movements of time, of the daily work of life, of its perplexities and contradictions, we should lift our gaze fearlessly to the clear vault of heaven, and seek ever to obtain a firmer grasp of and a keener insight into the origin of all goodness and beauty, the capacities of our own hearts and minds, the intellectual fruits of mankind throughout the centuries, and the wondrous works of nature around us; at the same time remembering always that in humility alone lies true greatness, and that knowledge and wisdom are alone profitable in so far as our lives are governed by them.”
The career of Nicholas of Cusa is interesting, because it sums up so many movements, and, above all, educational currents in the fifteenth century. He was born in the first year of the century, and lived to be sixty-four. He was the son of a wine grower, and attracted the attention of his teachers because of his intellectual qualities. In spite of comparatively straitened circumstances, then, he was afforded the best opportunities of the time for education. He went first to the school of the Brethren of the Common Life at Deventer, the intellectual cradle of so many of the scholars of this century. Such men as Erasmus, Conrad Mutianus, Johann Sintheim, Hermann von dem Busche, whom Strauss calls ” the missionary of human wisdom,” and the teacher of most of these, Alexander Regius, who has been termed the schoolmaster of Germany, with Nicholas of Cusa and Rudolph Agricola and others, who might readily be mentioned, are the fruits of the teaching of these schools of the Brethren of the Common Life, in one of which Thomas a Kempis, the author of ” The Imitation of Christ,” was, for seventy years out of his long life of ninety, a teacher.
Cusanus succeeded so well at school that he wan later sent to the University of Heidelberg, and subsequently to Padua, where he took up the study of Roman law, receiving his doctorate at the age of twenty-three. This series of educational opportunities will be surprising only to those who do not know educational realities at the beginning of the fifteenth century. There has never been a time when a serious seeker after knowledge could find more inspiration. On his return to Germany, Father Krebs became canon of the cathedral in Coblenz. This gave him a modest income, and leisure for intellectual work which was eagerly employed. He was scarcely more than thirty when lie was chosen as a delegate to the Council at Basel. After this he was made Archdeacon of the Cathedral of Luttich, and from this time his rise in ecclesiastical preferment was rapid. He had attracted so much attention at the Council of Basel that he was chosen as a legate of the Pope for the bringing about certain reforms in Germany. Subsequently he was sent on ecclesiastical missions to the Netherlands, and even to Constantinople. At the early age of forty he was made a Cardinal. After this he was always considered as one of the most important consultors of the Papacy in all matters relating to Germany. During the last twenty-five years of his life in all the relations of the Holy See to Germany, appeal was constantly made to the wisdom, the experience, and the thoroughly conservative, yet. foreseeing, judgment of this son of the people, whose education had lifted him up to be one of the leaders of men in Europe.
It was during this time that he wrote most of his books on mathematics, which have earned for him a prominent place in Cantor’s ” _History of Mathematics,” about. a score of pages being devoted to his work. Much of his thinking was done while riding on horseback or in the rude vehicles of the day on the missions to which he was sent as Papal Legate. He is said to have worked out the formula for the cycloid curve while watching the path described by flies that had lighted on the wheels of his carriage, and were carried forward and around by them. His scientific books, though they included such startling anticipations of Copernicus’ doctrines as we have already quoted (Copernicus did not publish the first sketch of his theory for more than a quarter of a century after Cusanus’ death), far from disturbing his ecclesiastical advancement or injuring his career as a churchman, seem actually to have been considered as additional reasons for considering him worthy of confidence and consultation.
As the result of his careful studies of conditions in Germany, he realized very clearly how much of unfortunate influence the political status of the German people, with their many petty rulers and the hampering of development consequent upon the trivial rivalries, the constant bickerings, and the inordinate jealousies of these numerous princelings, had upon his native country. Accordingly, towards the end of his life he sketched what he thought would be the ideal political status for the German people. As in everything that Le wrote, he went straight to the heart of the matter and, without mincing words, stated just exactly what he thought ought to be done. Considering that this scheme of Cusanus for the prosperity and right government of the German people was not accomplished until more than four centuries after his death, it is interesting, indeed, to realize how this clergyman of the middle of the fifteenth century should have come to any such thought. Nothing, however, makes it clearer than this, that it is not time that fosters thinking, but that great men at any time come to great thoughts. Cusanus wrote:
” The law and the kingdom should be placed under the protection of a single ruler or authority. The small separate governments of princes and counts consume a disproportionately large amount of revenue without furnishing any real security. For this reason we must have a single government, and for its support we must have a definite amount of the income from taxes and revenues yearly set aside by a representative parliament and before this parliament (reichstag) must be given every year a definite account of the money that was spent during the preceding year.”
Cusanus’ life and work stand, then, as a type of the accomplishment., the opportunities, the power of thought, the practical scholarship, the mathematical accuracy, the fine scientific foresight of a scholar of the fryfteenth century. For us, in medicine, it is interesting indeed to realize that it is from a man of this kind that a great new departure in medicine with regard to the employment of exact methods of diagnosis had its first suggestion in modern times. The origin of that suggestion is typical. It has practically always been true that it was not the man who had exhausted, or thought that he had done so, all previous medical knowledge, who made advances in medicine for us. It has nearly always been a young man early in his career, and at a time
as yet, his mind was not overloaded with the medical theories of his own time. Cusanus was probably not more than. thirty when he made the suggestion which represents the first practical hint for the use of laboratory methods in modern medicine. It came out of his thoughtful consideration of medical problems rather than from a store of garnered information as to what others thought. It is a lesson in the precious value of breadth of education and serious training of mind for real progress at all times.