THE PRACTICAL VALUE OF PURE SCIENCE 235 



It would be well worth while to stop to consider how much the 

 various branches of engineering owe to pure mathematics and pure 

 physics; or to relate the rise of numerous great industries that have 

 grown out of the theoretical study of chemistry. Where would be our 

 electric lighting and transportation but for the explanations of Frank- 

 lin, Volta and Faraday ? But I will limit myself to the practical value 

 of pure science as exemplified by a particular one, biology. In making 

 this restriction I should add that history tells how each of the pure 

 sciences has led to useful ends, so that biology is but one of several 

 cooperating sisters, each making her contribution to greater human 

 happiness. 



Biology has to explain the nature of living energies in treating of 

 animals and plants and of man himself. Biology has to interpret 

 processes, and this it attempts to do in a variety of ways accordiug 

 to the nature of the problem, the material and the bias of the thinker. 

 Biology has to some extent grown up side by side with medicine; each 

 helped the other in the days of their beginnings, and for that reason 

 we may first treat its practical bearings to medicine. 



In the seventeenth century the microscope came into use and it 

 opened up, in the hands of Leeuwenhoek and Schwammerdamm, a 

 wealth of unexpected detail. Leeuwenhoek exhibited his dissection of 

 an ant to the delighted eyes of a king; since that time the tastes of 

 royalty seem to have deteriorated. But such discoveries in the finer 

 details of anatomy only presented new problems. The partial expla- 

 nation came in 1838 with Schleiden and the following year with 

 Schwann, who stated that animals and plants are built up of definite 

 living units, the cells; that such units compose the tissues that had 

 been determined by the physiologist Bichat, and that the organs are 

 composed of definite layers of cells. The simplest animals, what we 

 now call the Protozoa, were shown by Dujardin to be each composed 

 of only a single cell. We define a cell as a particular mass of living 

 substance regulated by a particular center, the nucleus. This view 

 was strengthened by the notable researches of particularly von Kolliker 

 and Max Schultze, and so gradually extended to all animals and plants 

 as well as to the human body. Eduard van Beneden later finally 

 settled the fact that the egg, the beginning of each many-celled animal, 

 is itself a single cell. Thus biologists have come to concentrate their 

 attention upon cell activities, and this cell unit has proved as fruitful 

 in biology as the atom in chemistry, though the cell is something vastly 

 more complex than many atoms. Now there grew up with this new 

 doctrine Rudolf Virchow, the great master of the study of disease, and 

 he it was who by placing the study of disease upon the cellular basis, 

 by tracing diseased conditions to particular cells, laid the rational foun- 

 dation of one branch of modern medicine. The investigation of the 



