462 GROWTH OB" BIOLOGY IN THE NINETEENTH CENTURY. 



of our mind, thereby to make them serviceable to our welfare in count- 

 less waj's, or where they confront us as hostile powers to defend our- 

 selves from them by hygienic protective measures. But what is much 

 more important, biology enlightens us concerning our own human 

 nature, l)oth in its corporeal and in its spiritual aspects, and conse- 

 quentl}" leads to a greater mastery over ouiselves; and in accordance 

 with the progress of that knowledge biology influences even our 

 religious, moral, and social ideas, and thereby arouses woi'ld-moving 

 forces which have a no less transforming efl'ect on the conduct of our 

 life than does the expert mastery over inanimate nature, made possible 

 by physics and chemistry. 



The endless realm of biology is nuich more extensive than the chem- 

 ico-physical sciences. For that reason, in the brief time during which 

 1 can venture to beg your attention 1 can only give a summary review 

 of the development of the science during the nineteenth century, and 

 can only refer to those particular dii-ections in which our biological 

 knowledge has made its principal progress. 



A short definition can scarcely express correctly what a living being 

 is, or what life is. It can only be said that life depends upon a special, 

 peculiar organization of matter, and that with this organization are 

 connected special functions (Verrichtungen oder Functionen) which 

 are never met with in lifeless nature. The particular branches of sci- 

 ence which relate to the study of animals and plants are, therefore, 

 commonly divided into two groups, the anatomical and physiological 

 sciences; that is to sa}', into those which deal with the structure or 

 organization of the being and those which relate to its functions and 

 its life processes. 



In both directions our knowledge has been infinitely extended during 

 the century. While the sixteenth and seventeenth centuries brought 

 the great anatomists, an Eustachius. a Fallopia, a Vesalius, who, with 

 knife and scissors, opened for us a glimpse into the numerous organs 

 of the human body, biology in the nineteenth centui}"^ has achieved its 

 greatest victory in the province of microscopic anatomy. Equipped 

 with the compound microscope, that wonderful instrument which emi- 

 nent opticians have brought to the highest degree of efhcienc}^, the 

 anatomists were now in a position to discover a new and previously 

 unsuspected world of life. 



I believe, without hesitation, that I must indicate as one of the great- 

 est acquisitions of biology during the nineteenth century the discovery 

 that plants and animals are built up of cells, or, speaking in general 

 terms, of innumerable minute elementary organisms. By the joint 

 labors of famous biologists — I will name only Purkinje, vSchleiden and 

 Schwann, Hugo von Mohl, Niigeli, Remak, KoUiker and Virchow, 

 Briicke, Cohn, and Max Schultze — our knowledge of the organization of 

 living substance has been infinitely broadened and deepened. Anatomy 



