Of course, it is difficult for present-day scientists to imagine a man exhausting the whole round of science in this way. Many who have read but little more than the titles of Father Kircher's many books are accordingly prone to speak of him as a mine of information, but without any [{126}] proper critical judgment. He has succeeded, according to them, in heaping together an immense amount of information, but it is of the most disparate value. There is no doubt that he took account of many things in science that are manifestly absurd. Astrology, for instance, had not, in his time, gone out of fashion entirely, and he refers many events in men's lives to the influence of the stars. He even made rules for astrological predictions, and his astronomical machine for exhibiting the motions of the stars was also meant to be helpful in the construction of astrological tables. It must not be forgotten, however, that in his time the best astronomers, like Tycho Brahe and even Kepler, had not entirely given up the idea of the influence of the stars over man's destiny.
As regards other sciences, there are details of information that may appear quite as superstitious as the belief in astrology. Kircher, for instance, accepted the idea of the possibility of the transmutation of metals. It is to be said, though, that all mankind were convinced of this possibility, and indeed not entirely without reason. All during the nineteenth century scientists believed very firmly in the absolute independence of chemical elements and their utter non-interchangeability. As the result of recent discoveries, however, in which one element has apparently been observed giving rise to another, much of this doctrine has come to be considered as improbable, and now the idea of possible transmutation of [{127}] metals and other chemical elements into one another appears not so absurd as it was half a century ago.
Any one who will take up a text-book of science of a century ago will find in it many glaring absurdities. It will seem almost impossible that a scientific thinker, in his right senses, could have accepted some of the propositions that are calmly set down as absolute truths. Every generation has made itself ridiculous by knowing many things "that are not so," and even ours is no exception. Father Kircher was not outside this rule, though he was ahead of his generation in the critical faculty that enabled him to eliminate many falsities and to illuminate half-truths in the science of his day.
Undoubtedly the most interesting of Father Kircher's scientific books is his work On the Pest, with some considerations on its origin, mode of distribution, and treatment, which about the middle of the seventeenth century gathered together all the medical theories of the times as to the causation of contagious disease, discussed them with critical judgment and reached conclusions which anticipate much of what is most modern in our present-day medicine. It is this work of Father Kircher's that is now most often referred to, and very deservedly so, because it is one of the classics which represents a landmark in knowledge for all time. It merits a place beside such books as Harvey on the Circulation of Blood, or even Vesalius on Human [{128}] Anatomy. As we have seen, it is now quoted from by our best recent authorities who attempt seriously to trace the history of the microbic theory of disease, and its conclusions are the result of logical processes and not the mere chance lighting upon truth of a mind that had the theories of the time before it. In it Father Kircher's genius is best exhibited. It has the faults of his too ready credibility; and his desire to discuss all possible phases of the question, even those which are now manifestly absurd, has led him into what prove to be useless digressions. But on the whole it represents very well the first great example of the application of the principle of inductive science to modern medicine. All the known facts and observations are collected and discussed, and then the conclusions are suggested.
It is very interesting to trace the development of Father Kircher's ideas with regard to the origin, causation, and communication of disease, because in many points he so clearly anticipates medical knowledge that has only come to be definitely accepted in very recent times. It has often been pointed out that Sir Robert Boyle declared that the processes of fermentation and those which brought about infectious disease, were probably of similar nature, and that the scientist who solved the problem of the cause of fermentation would throw great light on the origin of these diseases. This prophetic remark was absolutely verified when Pasteur, a chemist who had solved the problem of fermentation, also solved [{129}] the weightier questions connected with human diseases. Before even Boyle, however, Father Kircher had expressed his opinion that disease processes were similar to those of putrefaction. He considered that putrefaction was due to the presence of certain corpuscula, as he called them, and these he said were also probably active in the causation of infectious disease.
He was not sure whether or not these corpuscula were living, in the sense that they could multiply of themselves. He considered, however, that this was very probable. As to their distribution, he is especially happy in his anticipations of modern medical progress. While he considered it very possible that they were carried through the air, he gives it as his deliberate opinion that living things were the most frequent agents for the distribution of the corpuscles of disease. He is sure that they are carried by flies, for instance, and that they may be inoculated by the stings of such insects as fleas or mosquitoes. He even gives some examples that he knew of in which this was demonstrated. Still more striking is his insistence on the fact that such a contagious disease as pest may be carried by cats and dogs and other domestic animals. The cat seemed to him to be associated with special danger in this matter, and he gives an example of a nunnery which had carefully protected itself against possible infection, but had allowed a cat to come in, with the result that some cases of the disease developed.
An interesting bit of discussion is to be found in the chapter in which Father Kircher takes up the consideration of the problem whether infectious disease can ever be produced by the imagination. He is speaking particularly of the pest, but there is more than a suspicion that under the name pest came at times of epidemics many of our modern contagious diseases. Father Kircher says that there is no doubt that worry plays an important role in predisposing persons to take the disease. He does not consider, however, that it can originate of itself, or be engendered in the person without contact with some previous case of pest. With regard to the question of predisposition he is very modern. He points out that many persons do not take the disease, because evidently of some protective quality which they possess. He is sure, too, that the best possible protection comes from keeping in good, general health.
A curious suggestion is that with regard to the grave-diggers and undertakers. It has often been noted in Italy, so Father Kircher asserts, that these individuals as a rule did not succumb to the disease, notwithstanding their extreme exposure, when the majority of the population were suffering from it. Toward the end of the epidemic, however, at the time when the townspeople were beginning to rejoice over its practical disappearance, it was not unusual to have these caretakers of the dead brought down with the disease--often, too, in fatal form. Father [{131}] Kircher considers that only strong and healthy individuals would take up such an occupation. That the satisfaction of accomplishing a large amount of work and making money kept them in good health. Later on, however, as the result of overwork during the time of the epidemic and also of discouragement because they saw the end of prosperous times for them, they became predisposed to the disease and then fell victims.
With regard to the prevention of the pest in individual cases, Father Kircher has some very sensible remarks. He says that physicians as a rule depend on certain medicinal protectives or on amulets which they carry. The amulets he considers to be merely superstitious. The sweet-smelling substances that are sometimes employed are probably without any preventive action. Certain physicians employed a prophylactic remedy made up of very many substances. This is what in modern days we would be apt to call a "gunshot prescription." It contained so many ingredients that it was hoped that some one of them would hit the right spot and prove effective. Father Kircher has another name for it. We do not know whether it is original with him, but in any case it is worth while remembering. He calls it a "calendar prescription," because when written it resembled a list of the days of the month.