PHYSIOLOGY Ol TO-DAY 



the most fascinating stories of the last quarter of a century 

 and has depended, to a large extent, upon chemical methods 

 for its advance. 



The results from the application of physical methods to 

 the problems of physiology, although not so spectacular 

 and generally recognized as those of the biochemical 

 school, have nevertheless been of immense theoretical 

 importance, and promise to be even more valuable in the 

 future.' The advances in the mechanical aspects of muscular 

 contraction, the investigation of the heat production of 

 isolated muscles under varying conditions, and the appli- 

 cation of newer physical methods to the study of the 

 nervous impulse and the electrical change in nerve dur- 

 ing activity may serve as a few examples of this type of 

 approach to physiological problems. 



A third method of attack, the method of Harvey, is 

 as old as our science itself, and still must hold an important 

 place in the immediate future. This is what we may call 

 the purely physiological method. Careful anatomical 

 considerations, experiments on living animals, deductions 

 from these experiments, more experiments to test these, 

 and so forth, characterize it. Within the past decade or 

 so, our knowledge of the importance of the capillaries in 

 the dynamics of the circulation, of the functions and 

 interrelations of many parts of the brain and central 

 nervous system, and of the relation of the emotions to 

 bodily functions — to mention only a few examples — has 

 been enormously amplified by the use of the purely phys- 

 iological method. 



With the increasing interest, which we have mentioned, 

 in regard to the physiology of the animal as a whole as 

 opposed to a study of its systems and organs separately, 

 a beginning has been made in building up what we may 

 call human physiology, where the experiments have been 

 carried out on man himself. In the fields of metabolism 



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