His sole recreation was to go in search of insects in the little soil which Holland offers above the waters. The melancholy meads, covered with Paul Potter's herds, possess, in the moist warmth of the summer, a great variety of animal life. The traveller is much impressed when he sees the crane, the stork, and the crow, elsewhere hostile, reconciled here by the abundance of their food, which they frequently hunt in company on terms of perfect accord. Hence the landscape acquires a peculiar charm. The cattle assume an air of placid security which they do not elsewhere exhibit. The summer is short, and early assumes the gravity of autumn. Man and Nature--all appears of a pacific character, harmonized in a great moral sweetness and remarkable seriousness of mood. Enthusiastic collector as his father was, he grieved to see the youth of Swammerdam thus employed. It had been his ambition to make of his son a renowned minister who should shine in controversy, and an eloquent preacher. But his son seemed daily to grow more dumb. The chagrined father lowered his views from glory to money. In that golden city, so feverish and so diseased, no career is more lucrative than that of a physician. But here arose another difficulty. Swammerdam threw himself heartily into his medical studies; but on condition that he created them--as yet they did not exist. Therefore, the basis on which he desired to rest them was the preliminary creation of the natural sciences. How cure the sick man unless you understood the healthy? And how understand the latter without studying side by side the inferior animals which translate and explain disease? But can one see into such delicate mysteries with the eye alone? Does not the feebleness of the sense of vision lead us astray? The serious creation of science would suppose a reform of our senses and the creation of optics. A veritable creation! Look at the microscope. Is it a simple spy-glass? To the eyes which the instrument possessed, Swammerdam added two arms, one of which bears the glass and the other the object. He himself says, in reference to his more difficult investigations, "that he had attempted to obtain the assistance of another person, but that such assistance proved, in fact, an obstacle." It was for this reason that he organized a dumb man of copper, a discreet servant ready for every work; thanks to whom the observer disposes of supplementary hands and numerous eyes of different degrees of power. In the same manner as the birds expand or contract their visual organs, either to grasp objects in a whole or to scrutinize with searching glance the smallest detail, Swammerdam created the method of successive enlargement; the art of employing lenses of different sizes and varying curvature, which permit the observer to see _en masse_, and to study each separate portion, and finally to survey the whole for the purpose of properly replacing the details and reconstituting the general harmony.