THE SCIENCE OF BIOLOGY 431 



for some time; then with a discovery that illuminates the problem 

 more clearly, interest centers there and advances in our knowledge 

 are soon registered. Meanwhile other problems have slowed down 

 or become temporarily inactive, only to advance again later. Con- 

 spicuous among the contributions o£ the current century are: (a) 

 The development and refinement of the Mendelian interpretation 

 of heredity, with correspondingly rigorous study of the behavior 

 of the chromosomes, (b) The development of the concept that the 

 form of an animal results from a dominant-subordinate relationship 

 of parts during embryonic development and in regeneration, (c) 

 The transformation of more or less casual methods of Nature Study 

 into a science, now known as Ecology, utilizing the methods of pre- 

 cision in study of the relation between the organism and its sur- 

 roundings, (d) Increasingly rigorous examination of the physico- 

 chemical nature of protoplasm and its energy-transforming processes 

 in development, irritability, contractility, secretion, and other phe- 

 nomena that characterize life, (e) The development and study of 

 the role played by vitamins. (/) The development of the study of 

 the endocrine glands and the nature and action of hormones. No 

 doubt these trends will determine the nature of progress in the 

 immediate future. 



Abstract and Applied Biology. One may divide the Bio- 

 logical Sciences into two lines of interest: (i) Studies that are pur- 

 sued for the sole purpose of adding to the sum of human knowledge 

 and thus gratifying Man's age-old instinct to project order into the 

 world about him; one speaks of such interests as Abstract Biology; . 

 (2) The application of biological principles to human affairs, 

 known as Applied Biology. However, there is no sharp nor well- 

 defined line separating the two. For Applied Biology draws much 

 of its technical and all of its theoretical methods and concepts from 

 academic work, and Abstract Biology frequently looks to the Ap- 

 plied for fact and confirmation of theory and for new problems. In 

 this treatment we have for the most part concerned ourselves with 



