[Sidenote: Cardan, 1501-76]
As one turns the pages of the numerous works of Jerome Cardan one is astonished to find the number of subjects on which he wrote, including, in mathematics, choice and chance, arithmetic, algebra, the calendar, negative quantities, and the theory of numbers. In the last named branch it was another Italian, Maurolycus, who recognized the general character of mathematics as "symbolic logic." He is indeed credited with understanding the most general principle on which depends all mathematical deduction.[1] Some of the most remarkable anticipations of modern science were made by Cardan. He believed that inorganic matter was animated, and that all nature was a progressive evolution. Thus his statement that all animals were originally worms implies the indefinite variability of species, just as his remark that inferior metals were unsuccessful attempts of nature to produce gold, might seem to foreshadow the idea of the transmutation of metals under the influence of radioactivity. It must be remembered that such guesses had no claim to be scientific demonstrations.
The encyclopaedic character of knowledge was then, perhaps, one of its most striking characteristics. Bacon was not the first man of his century to take all knowledge for his province. In learning and breadth of view few men have ever exceeded Conrad Gesner, [Sidenote: Gesner] called by Cuvier "the German Pliny." His History of Animals (published in many volumes 1551-87) was the basis of zoölogy until the time of Darwin. [Sidenote: Zoölogy] He {612} drew largely on previous writers, Aristotle and Albertus Magnus, but he also took pains to see for himself as much as possible. The excellent illustrations for his book, partly drawn from previous works but mostly new, added greatly to its value. His classification, though superior to any that had preceded it, was in some respects astonishing, as when he put the hippopotamus among aquatic animals with fish, and the bat among birds. Occasionally he describes a purely mythical animal like "the monkey-fox." It is difficult to see what criterion of truth would have been adequate for the scholar at that time. A monkey-fox is no more improbable than a rhinoceros, and Gesner found it necessary to assure his readers that the rhinoceros really existed in nature and was not a creation of fancy.
[Sidenote: Leonardo]
As the master of modern anatomy and of several other branches of science, stands Leonardo da Vinci. It is difficult to appraise his work accurately because it is not yet fully known, and still more because of its extraordinary form. Ho left thousands of pages of notes on everything and hardly one complete treatise on anything. He began a hundred studies and finished none of them. He had a queer twist to his mind that made him, with all his power, seek byways. The monstrous, the uncouth, fascinated him; he saw a Medusa in a spider and the universe in a drop of water. He wrote his notes in mirror-writing, from right to left; he illustrated them with a thousand fragments of exquisite drawing, all unfinished and tantalizing alike to the artist and to the scientist. His mind roamed to flying machines and submarines, but he never made one; the reason given by him in the latter case being his fear that it would be put to piratical use. He had something in him of Faust; in some respects he reminds us of William James, who also started as a {613} painter and ended as an omniverous student of outré things and as a psychologist.
[Sidenote: Anatomy]
If, therefore, the anatomical drawings made by Leonardo from about twenty bodies that he dissected, are marvellous specimens of art, he left it to others to make a really systematic study of the human body. His contemporary, Berengar of Carpi, professor at Bologna, first did this with marked success, classifying the various tissues as fat, membrane, flesh, nerve, fibre and so forth. So far from true is it that it was difficult to get corpses to work upon that he had at least a hundred. Indeed, according to Fallopius, another famous scientist, the Duke of Tuscany would occasionally send live criminals to be vivisected, thus making their punishment redound to the benefit of science. The Inquisitors made the path of science hard by burning books on anatomy as materialistic and indecent.
[Sidenote: Servetus]
Two or three investigators anticipated Harvey's discovery of the circulation of the blood. Unfortunately, as the matter is of interest, Servetus's treatment of the subject, found in his work on The Trinity, is too long to quote, but it is plain that, along with various fallacious ideas, he had really discovered the truth that the blood all passes through heart and lungs whence it is returned to the other organs.
[Sidenote: Physics]