THE GROWTH OF BIOLOGICAL IDEAS 171 



not been crushed by Hoppe-Seyler, we should probably have 

 had this knowledge nearly forty years sooner. A useful lesson 

 can be learned from the sad story: under no circumstances 

 must research be controlled by authority. It is true that 

 Hoppe-Seyler had no legal authority, such as one scientist has 

 over another in a totalitarian state; yet his influence was suf- 

 ficient to retard by several decades the investigation of one 

 of the most fundamental problems of life. 



One cannot guess what branches of biology' are going to 

 develop most rapidly in the future, though one can surmise 

 that certain lines have been rather thoroughly ^vorked out 

 and offer poor prospects. Much may be expected from the 

 full incorporation of physiology into biology. In the past 

 animal physiology has been a sort of ancillary branch of medi- 

 cine, as botany was of pharmacology^ in the sixteenth century. 

 Plant physiology has never suffered under the same disadvan- 

 tages; it has developed naturally like the other branches of 

 botany and in concert with them, and is universally regarded 

 as a branch of botany. Zoology, greatly to its detriment, ^vas 

 for lono: resrarded as being^ concerned with all branches of 

 knowledge of animals except that of function. This idea was 

 as detrimental to physiology as to the major subject. A 

 change of outlook is at last manifesting itself. Physiologists 

 have begun to untie the strings that have bound them to 

 man, guinea pig, and frog. 



If physiology can break loose from subservience to medi- 

 cine and stand on its own legs, we may look for rapid progress 

 in our understanding of the processes of growth and differ- 

 entiation. These are tw^o of the most fundamental phenom- 

 ena of life. Until now they have been studied mostly by 

 biologists lacking special training in physiology, for profes- 

 sional physiologists have held aloof. Wilhelm Roux, son of 

 a fencinor instructor, founded the science of the mechanics of 

 development toward the end of the nineteenth century. The 

 embryological experiments carried out by the philosophic 

 Hans Driesch about the turn of the century led him to con- 

 clude that a purely mechanical and chemical explanation of 



