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Cusanus And The First Suggestion Of Laboratory Methods In Medicine

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 th
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 churchman, 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 beats of

the pulse were counted, should be weighed, and this weight compared with

that of the average weight of water 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 single 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 be absolutely at rest or, as he said, devoid of

all motion. His words are: Terra igitur, quae centrum esse nequit, motu

omni carere non potest. He described very clearly how the earth moved

round its own axis, and then he 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 fixa, sed movetur

ut aliae 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

contains, 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, he 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 made by the great Jesuit mathematician, Father Clavius. Perhaps

the work of Cusanus that is best known is that On Learned Ignorance--De

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 he 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 stems,

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


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 be 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 case, 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, perhaps, 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. He also thought

that the comparative weight of various roots, stems, 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 man 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 Hegius, 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 was 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

he was chosen as a delegate to the Council at Basel. After this he was

made Archdeacon of the Cathedral of Luettich, 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 he 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 fifteenth 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 when, 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