418 PHYSIOLOGICAL REGULATIONS 



may infer either that he is the unfortunate victim of a doctrinaire 

 theory as to how experimentation should proceed, or that the time, 

 material or equipment at his disposal is too limited to allow him to 

 give attention to more than one narrow aspect of his problem" 

 (Fisher, '37, p. 101). 



Adopting some components earlier discussed, an investigator 

 of athletic accomplishment might choose ten loads for simultaneous 

 study, as follows : 



{!) Water load, 0. 



(2) Water load, +0.5% of Bo. 



(3) Heat load, + 0.2 Cal./kg. 



(4) Heat load, + 0.5 Cal./kg. 



(5) Glucose load, 0. 



(6) Glucose load, -0.1 gm./kg. 



(7) Glucose load, + 0.2 gm./kg. 



(8) Heart frequency, + 20 per cent of resting, induced by 



epinephrine. 



(9) Heart frequency, +40 per cent of resting. 

 (10) Heart frequency, + 60 per cent of resting. 



Of the different combinations of the n loads taken 2 at a time, in 

 this case 45, 8 are mutually exclusive by definition, so that 37 ex- 

 periments at least are to be performed. In each state the human 

 subject runs 1 kilometer in the shortest time he can; these times 

 are correlated with each of the ten loads. For a more complete 

 answer, enough repetitions will be made to establish the statistical 

 significance of each combined physiological state in the perform- 

 ance of running. This is the explicit form, in the language of in- 

 crement, of myriads of investigations. 



In general, to evaluate n states characterized by diverse simulta- 

 neous loads, a plan is set up in which n{n-l){n-2) . . . /I. 2. 3. . . . 

 total combinations are studied. States that represent two or more 

 loads belonging to one component are precluded; leaving in the 

 above example 133 experiments. In each the investigator ascer- 

 tains the time required to run, and thereafter applies multiple 

 correlation, or some other technique of measuring association, to 

 the results, finally deriving a value for each of the combinations 

 of components. 



The usual scheme of combining loads is the Latin square, which 

 arranges all the possible combinations in a certain sequence that 



