Page:Popular Science Monthly Volume 58.djvu/578

observations upon the development of animals had progressed in 1672. His are, doubtless, the earliest figures ever made showing the comparatively early stages of development. Harvey's observations on development, published in 1631, were not accompanied by illustrations, and the sketches of Fabricius, ab aqua pendente, published in 1604, werefar surpassed* by Malpighi's, the youngest stages represented being much older than his.

Fig. 3 shows a group of selected sketches from different plates, but they fail to give an adequate idea of the extent of the work, taken as a whole. It is very interesting to note the figures showing the formation of the heart and aortic arches. The execution of the figures in this work is less coarse than those on the silkworm.

The embryological thought of his time was dominated by the theory of preformation or predelineation. Just as when we examine a seed, we find within an embryo plantlet, so it was supposed that the minute embryos of all animal life existed in miniature within the egg. Harvey had expressed himself against it, and the doctrine was overthrown by Wolff in the following century. Malpighi's position, however, was based on actual observation; he was not able to find by examination any stage in which there was no evidence of organization. Dareste says that he examined eggs in a very hot August, in which there is reason to believe that developmental changes had gone forward to a considerable degree. Be this as it may, the imperfection of his instruments and methods would have made it very difficult to have seen anything definitely in stages below twenty-four hours. As a result of his experience, he says:

"When we undertake to discover the principle of life of animals in the egg we are astonished to find the animal already formed there; thus our labor is vain, for as soon as we encounter the first movement of life we are obliged to recognize parts that are visible to our eyes. * * * On this account, it may be necessary to declare that the first beginnings preexist in the egg," etc. In his posthumous works he "is less circumspect, and goes even to the point of describing the mechanism of evolution of these primitive elements."

Malpighi was a naturalist, but of a new type; he began to look below the surface, and essayed a deeper level of analysis, in observing and describing the internal and minute structure of animals and plants, and when he took the further step of investigating their development he was anticipating the work of the nineteenth century.

 

JOHN SWAMMERDAM. 1637-1680.

Swammerdam was a different type of man—nervous, incisive, very intense, stubborn and self-willed. Much of his character shows in the