6Z IOWA ACADEMY OF SCIENCES. 



probably because of the nature of the problems involved, 

 the validity of a conclusion is established with greater 

 difficulty and less certainty as to its correctness than in 

 many a physical research, for instance. This is no doubt 

 owing to the greater difficulty in arranging experiments 

 that shall exclude all but a certain number or group of 

 forces and agencies from the action to be observed. This 

 condition calls for ingenuity of the highest order, and 

 demands patience without limit. But this peculiarity of 

 biological research emphasizes the need of frequently recur- 

 ring to the consideration of physical methods of excluding 

 from an experiment all but certain known and definite 

 influences, and of the relentless rigor with which the 

 physicist has been compelled to learn to cast out all evi- 

 dence which can be at all called into question. As the 

 biologist has advanced in the manner and direction here 

 indicated he has penetrated deeper into those elusive 

 unknowns which are of so much interest and concern to 

 us, and which obscure the ever interesting problems in 

 regard to the processes of life and the mechanism of vital 

 actions. 



The debt which physics owes to the other sciences is un- 

 questionably great, whether regard is had to the material 

 aids in research that have been borrowed by physicists, or 

 whether one considers the problems furnished, or the sug- 

 gestions of methods of work that have come from the 

 discoveries, or even the failures of other investigators. 



But physics stands in the relation of an elder sister to 

 the other branches. This department of science has 

 enjoyed the privilege of first establishing and defending 

 the methods and criteria which must surely prevail until 

 science shall undergo some radical and now unsuspected 

 change in its essentials. Until such a time arrives, physics 

 will continue to be at once the most severely exact of the 

 sciences and the one among them whose privilege it is to 

 lend and to give in the most unstinted measure both 

 methods and means for their growth and perfection. 



The object of all devotees of science is the same; truth — 

 the truth in regard to nature, that nature and natural 



