Page:Popular Science Monthly Volume 31.djvu/533

Rh in a perfect network of curious cross-relationships. Lizards that were almost crows, marsupials that were almost ostriches, insectivores that were almost hats, rodents that were almost monkeys, have come at the very nick of time to prove the truth of descent with modification. Among the most interesting of these strange coincidences are such episodes as the discovery in the rivers of Queensland of that strange lung-bearing and gill-breathing fish, the barramunda, only known before in the fossil form as a long-extinct species, but in whose anatomical structure Günther has discerned the missing link between the antique ganoid type of fishes on the one hand, and the mud-fish and salamandroid amphibians on the other.

In the practical applications of biological and physiological science to the wants and diseases of human life two at least deserve mention here. Anæsthetics are almost entirely a growth of our half-century: chloroform was first employed in operations by Simpson in 1847, and the use of other similar agents is still more recent. Again, the discovery that zymotic diseases in men and animals are due to the multiplication within the body of very minute organisms, known as microbes, bacteria, or bacilli, now promises to revolutionize medical science. Their connection with decomposition was still earlier detected. The names of Pasteur, Tyndall, and Koch are specially identified with researches into the nature of these tiny morbid organisms and the best means of preventing or neutralizing their attacks, either on living or dead matter.

In marvelous contrast to the fragmentary and disjunctive science of fifty years ago, modern science at the present day offers us the spectacle of a simple, unified, and comprehensible cosmos, consisting everywhere of the same prime elements, drawn together everywhere by the same great forces, animated everywhere by the same constant and indestructible energies, evolving everywhere along the same lines in accordance with the self-same underlying principles. It shows us the community of ultimate material in sun and star, in nebula and meteor, in earth and air and planet and comet. It shows us identical metals and gases in fiery photosphere and in electrically-heated matter in our own laboratories. It shows us atoms of hydrogen or of sodium pulsating rhythmically with like oscillations in star-cloud or sun-cloud, and in London or Berlin. It exhibits to our eyes or to our scientific imagination a picture of the universe as a single whole, a picture of its evolution as a continuous process—one type of matter diffused throughout space; one gravitative attraction binding it together firmly in all parts; one multiform energy quivering through its molecules or traversing its ether, in many disguises of light, and heat, and sound, and electricity. It unfolds for us in vague hints the past of the universe as a diffuse mass of homogeneous matter, rolling in upon its local centers by gravitative force, and yielding up its primitive energy of separation as light and heat to the ethereal medium.