432 ELEMENTS OF BIOLOGY 



the abstract aspects o£ Animal Biology. We are therefore now in 

 position to appreciate in a broad way some of the practical applica- 

 tions of the science. 



Unlike Physics and Chemistry, the establishment of newly discov- 

 ered principles of Animal Biology does not afiFord bases for spec- 

 tacular inventions of mechanical devices and labor-saving tools and 

 processes. Applied Biology c?n employ the principles of the science 

 in a limited number of ways: (a) to increase human life span by 

 improving health and preventing disease; (b) to increase the quan- 

 tity and quality of food. While examples of the practical application 

 of biological principles in both of these fields are abundant, the 

 progress of Applied Biology until recent years has been relatively 

 slow. In spite of the fact that our knowledge of the principles that 

 actuate life processes is very incomplete, the world has at hand a 

 tremendous storage of biological fact and known principles which 

 have not yet been converted to practical use. This reservoir of theory 

 and fact is constantly growing and is being constantly tapped by 

 Applied Biology as it continues to increase in importance in human 

 affairs. 



In this discussion the history of the application of abstract prin- 

 ciples to human welfare does not concern us; we purpose only to 

 indicate the directions in which Abstract Biology has been of prac- 

 tical value and has influenced the daily life of civilized Man. 



Medicine has both an academic, or abstract, and a practical value. 

 The public is almost wholly interested in its practical applications, 

 however, and does not commonly think of its indebtedness to the 

 pursuit of knowledge for its own sake. A detailed statement of in- 

 debtedness, or even of a part thereof, would be out of place here, 

 even if it could be given. It is sufficient to indicate the fields in 

 which accomplishments in Abstract Biology have accompanied and 

 contributed to accomplishment in the art of medicine. 



Studies of metabolism in relation to growth and maintenance 

 made upon small mammals resulted in the identification of the 



