ks 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