PHYSIOLOGY OF TO-DAY 



ing, or partly isolating, the particular organ in question. 

 The former, which has been called the analytic method 

 of experimentation in contrast to the latter, or synthetic, 

 method, has the great advantages that normality is main- 

 tained — but at the expense of a control of variables — and 

 furthermore, that it can be applied to the human subject 

 The latter method, while sacrificing normality, admits 

 of a much better control of the variable factors which 

 enter into the experiment. 



In the past, a great deal of knowledge has accumulated 

 concerning the function and mode of operation of the 

 separate organs of the animal organism; but, owing 

 probably to the use of the synthetic method, it is difficult 

 to bring all these observations and generalizations into 

 harmony with the physiology of the organism as a whole, 

 of the normal, healthy, everyday man. And it is becoming 

 increasingly evident that the physiology of the organism 

 as a whole is not simply the sum of the functions of the 

 constituent organs or parts. There exists among all the 

 parts a finely balanced regulation, which always operates 

 in such a way that the individual organs or systems cannot 

 work separately in the body, but must be correlated 

 together or integrated into a unity; for the animal must 

 function as a unit — an individual. This phase of our subject 

 is so vital that it will be well to illustrate what is meant 

 by an example. 



Let us see how an animal reacts to a change in its envi- 

 ronment which demands movement— the seeking of food, 

 fighting, or flight from some serious danger. Let us take 

 an extreme case, such as where maintenance of life demands 

 the most violent muscular movement of which the organ- 

 ism is capable. In the change from rest to violent muscular 

 exercise two things are necessary for the acting muscles: 

 oxygen and a readily oxidizable foodstuff to supply energy 

 for the movement. To supply these, many organs or systems 



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