432 A CENTURY OF SCIENCE 



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- 

 inated man's struggle against opposing forces would be 

 in large measure overcome. The results of recent work 

 in economic zoology, both in regard to the destruction of 

 enemies and protection of useful mammals, birds and 

 fishes, furnish a bright outlook for the future. 



Protozoology. Partly as an experimental field for the 

 solution of general biological problems and partly 

 because of its practical applications the study of protozoa 

 has now developed into a special science. 



The results of the investigations of Calkins, Woodruff, 

 Jennings and others have greatly supplemented our 

 understanding of the signification of such important 

 biological phenomena as reproduction, sexual differen- 

 tiation, conjugation, tropisms, and metabolism. 



