SELECTION OF SUBJECTS. 41 



rise in metabolism with every man. The ingestion of 200 grams of 

 beef Ukewise produces a rise in metabolism with every man. On the 

 other hand, when the quantitative relationship between the amounts of 

 sugar and beef ingested and the rise in metabolism are to be considered, 

 one may then state properly that experiments on one man are not per- 

 missible for a fundamental generalization. It has been the custom of 

 this Laboratory to recognize the legality of this latter contention and 

 a large number of experiments are always made in all our researches. 

 In fact, the Laboratory has even been charged with making too many 

 experiments.^ 



It is evident, however, that with a problem of such national impor- 

 tance, the study, to be of practical value, must be carried out with a 

 sufficiently large number of men for the results to be reasonably 

 conclusive. As our research on the effect of a reduced diet would 

 probably continue 3 or 4 months, it was necessary to select enough 

 men to allow for all exigencies which might arise, including possible 

 demands for national service. After careful consideration it was decided 

 that the investigation should begin with not less than 12 subjects. 



To secure results of general applicability to the civiUan population of 

 the United States, an ideal study would include observations not only 

 upon men but likewise upon women and children, but it was believed 

 that if one selected class was followed with great care, it could be 

 reasonably inferred that the general picture obtained would probably 

 in large part apply to other groups. Hence groups of young men were 

 decided on, these to be preferably beyond the age of growth. While in 

 the strictest sense growth persists until 28 years of age, which is shown 

 to be the average age for maximum height, we considered that college 

 students would meet the requirements perfectly. 



ESSENTIALS FOR SELECTION. 



In the selection of these men there were several essentials to be 

 observed. These may be outlined as follows : 



(1) They should be in good health. — It has been our custom to con- 

 sider subjects ''presumably in good health" as normal individuals, 

 from whom general deductions could be drawn. In this case we felt it 

 desirable to qualify the clause ''presumably in good health" with a 

 certification by a responsible physician after careful clinical examina- 

 tion. With these precautions we are able to state that our subjects 

 were normal young men and in good health. While it was the inten- 

 tion to avoid the age of growth and we supposed that our young men 

 were all of legal age, ^. e., 21 years or over, in certain instances men as 

 young as 19 years were inadvertently selected. Still we think this does 

 not vitiate our general contention that in this study we are not deal- 

 ing with the growth factor in any sense. 



1 Lindhard, Arch. f. d. ges. Physiol., 1915, 161, p. 345. 



