BIOLOGY IN HUMAN AFFAIRS 



and energy exchange of the body, of circulation, of respira- 

 tion, of the physiology of muscular exercise, of digestion 

 and of excretion, considerable bodies of facts exist for the 

 human subject, and certain generalizations have been 

 attempted. This trend in physiology is of tremendous 

 importance to medicine, but has been necessarily limited 

 by the lack of methods suitable for use on the human being. 

 As such methods are being constantly sought and found, 

 this side of physiology will probably yield a rich 

 harvest. 



Lastly, in considering the general methods of attack 

 upon their problems used by physiologists, one sees 

 clearly, although very faintly, a reconciliation being 

 brought about with zoology. An increasing interest in 

 so-called general physiology — or the physiology common 

 to all organisms as opposed to the special physiology of 

 any particular species — the awakening of zoologists to 

 the functional side of their science, and the use of compara- 

 tive physiological data to solve functional problems in the 

 higher animals, all tend to indicate that a real comparative 

 physiology may soon be flourishing along with other 

 developments. 



In a more concrete way, we may ask just what are the 

 problems of function and just how are they attacked and 

 partially solved? No better way of answering these ques- 

 tions can be found than by giving in some detail a few 

 examples of how physiologists go about their job. These 

 examples have been chosen from fields of work with which 

 the author feels some familiarity; equally satisfactory 

 examples could have been taken from many other provinces 

 of the science. 



Let us take first as an illustration a problem in connection 

 with the circulation of the blood, a problem of first im- 

 portance in this realm and one which was clearly grasped 

 by the discoverer of the circulation himself. Thus, over 



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