GROWTH OF BIOLOGY IN THE NINETEENTH CENTURY. 465 



the simplest living beings take their origin direct from lifeless nature. 

 Just as in the eighteenth century intestinal worms and infusoria, 

 also formerly called infusion-animalcuhu (Aufgusstliierchen), were sup- 

 posed to arise by ^'equivocal generation." so at a later date bacteria 

 and allied microbes, because they seemed so very small and simple, 

 and so suddenly invaded liquids without anybody's knowing whence 

 they came, were supposed to be so formed. It was not one of the 

 smallest services which Pasteur rendered, that he irrefutably proved, 

 by scientific methods, that for microbes, too, the saying is fultilled, 

 " Omne vivum e vivo," life comes only from life. By Pasteur's experi- 

 ments we know that the germs of those organisms are everywhere 

 more or less abundantly distributed in water, air, and earth. 



In the doctrine of cells, too, in its first form, the idea of spontaneous 

 generation made a pernicious nest, for, according to the view of 

 Scheiden and Schwann, new cells arise in the bodies of animals and 

 plants by a sort of crystallization from a nutritive solution, either 

 within or without mother cells. The truth that the increase takes 

 place solely b}- propagation by division was first made out by weari- 

 some labor by the admiral^le investigations of Mohl and Nageli, of 

 Remak, Kolliker, and Virchow, and many other students, and raised 

 to the rank of a universal biological law: "Omnis cellula e cellula." 



It may be broadly said that, in spite of all the progress of science, 

 the chasm between living and lifeless nature, instead of graduall}' 

 closing up, has, on the contrary, become deeper and wider. More 

 thorough study, aided bj" philosophical intuition, teaches year l)v 

 3^ear more distincth^' that the cell, that elementary bed rock of living 

 nature, is far from being a peculiar chemical giant molecule, oi- living 

 albumen, and as such destined to become the subject of the chemistry 

 of the future. The cell is itself an organism, compounded from numer- 

 ous still smaller vital units. They are of various chemical composi- 

 tion, and are bound together through relations to the vital process of 

 the cells unknown to us. Here lies hidden a world of minute life for 

 the investigation of which the power of our microscopes and usual 

 methods of research fall short, but which, we will hope, a biology of 

 the future, with more perfect instruments and methods, may attain. 



A beginning has been made by the elaboration of the method of 

 staining, which we may expect to be extraordinarily perfected and its 

 powers to be greatly increased. To this we must- add the insight 

 which the investigations of Butschli, Strasburger, Flemming. van 

 Beneden, and many others have aflorded of the facts (vorgang) of the 

 division of nuclei and cells. In karyokinesis we see how, at certain 

 times, minute parts in the cell of diverse chemical nature, such as cen- 

 trosomes, spindle filaments, chromosomes, nucleoles, and protoplasm 

 tracts are distinguishable, and how, impelled by enigmatical forces, 



