Coe — A Century of Zoology in America. 393 



Tropisms and Instincts. — Another field of experimen- 

 tal biology concerns the analysis of behavior of organ- 

 isms in response to various forms of stimuli. These 

 studies are being prosecuted on all groups of organisms, 

 including the larval stages of many animals, and are 

 yielding most remarkable results. The success in this 

 field of research is largely due to stimulating influence of 

 Jacques Loeb, Parker, Jennings, and their co-workers. 



Biological Chemistry. — Still another experimental field 

 which has developed into one of the most important of 

 the biological sciences relates to the fundamental chem- 

 ical and physical changes which underlie all organic phe- 

 nomena. A knowledge of both physiological and physi- 

 cal chemistry is to-day essential for all advanced 

 biological work. The peculiar nature of life itself, of 

 growth, disease, old-age, degeneration, death and dissolu- 

 tion are presumably only manifestations of chemical and 

 physical laws. The ultimate goal of all experimental 

 biology, therefore, will be reached only when the basic 

 physico-chemical properties of life are understood. At 

 that time only will the perennial controversy between 

 vitalism and mechanism be ended. 



Economic Zoology. 



A moment's reflection will show that economic 

 biology is the most essential of all sciences to the human 

 welfare and progress. For man's relation to his envi- 

 ronment is such that the penalty for ignorance or neg- 

 lect of the biological principles involved in the struggle 

 for existence quickly overwhelms him with a horde of 

 parasites or other enemies. 



It is only by the intelligent application of biological 

 knowledge that our food supplies, our forests, our domes- 

 ticated animals and our bodies can be protected from the 

 ever ravenous organisms which surround us. 



The losses to food supplies and other products by 

 insects alone amounts to 100 millions of dollars a month 

 in the^ United States. And the parasites cause losses in 

 sickness and premature deaths each year of many mil- 

 lions more. Then there are the destructive rodents and 

 other animals which add largely to our burdens of sup- 

 port. These enemies next to wars and fungi are the most 

 destructive agencies on earth. Could they but be elim- 



