458 POPULAR SCIENCE MONTHLY. 



The central topic about which this doctrine is elaborated is that of 

 adolescence — that specialized, reconstructive period fraught with the 

 highest possibilities and the severest risks for the future of the indi- 

 vidual, and representing nature's point of emphasis in the perspective 

 of human and racial development. The volumes accordingly con- 

 stitute in the first place an encyclopedia of adolescence. They bring 

 together with a degree of completeness quite unattempted hitherto, the 

 main data concerning the natural history of this period of unfoldment, 

 on its physical, physiological and psychological sides. The normal 

 growth of the body, the special development of different portions 

 thereof concerned with adolescence, the variations from such normal 

 development and their aberrations in disease and crime, the great role 

 that periodicity plays in human growth — these constitute the physical 

 basis which conditions through and through the nature of mental 

 growth, as well as determines the spirit of educational progressions. 

 The considerable aggregate of special studies that have been made in 

 all parts of this wide field are here carefully summarized; so that as 

 a book of reference the work takes a commanding position. There 

 will be a variety of opinion as to the specific and permanent value of 

 much of this evidence; and there may be some who will call into ques- 

 tion the validity of the question-sheet system by which much of the 

 psychological portion of the material has been gathered. Yet those 

 who weigh evidence in a fair spirit of criticism will find that on the 

 whole the weakness of certain types of evidence, for which unfor- 

 tunately we have no better substitute, is quite as clearly recognized by 

 the author as by themselves. It is easy enough to discredit the results 

 obtained by a somewhat miscellaneous set of answers to questions, many 

 of them rather difficult to answer with conscience and pertinence. But 

 here, as everywhere in statistical investigation, all depends upon the 

 temper and discretion that are used in the interpretation of the results. 

 If the method used for the extraction of the result is adapted to the 

 nature of the material, then it is likely that the investigation, however 

 deficient, has served a useful purpose. It is not necessary to defend the 

 questionnaire system in itself or the use which Dr. Hall and his pupils 

 have made of it; the real point of issue is how far such material will 

 stand the strain of the conclusions which are based thereupon. 

 Allowing for a wide divergence of opinion in this respect, there re- 

 mains a very considerable body of evidence which is tangible and well 

 classified, and in the aggregate has a significance in that it suggests 

 the trend of emphasis of the growth and distribution of mental traits. 

 It is difficult, indeed, to understand by what other means an equally 

 adequate conception of the contents, the impulses and the modes of 

 feeling of young minds could have been ascertained, or the larger 

 conclusions involved therein more saliently suggested. Nor must it be 

 supposed that Dr. Hall has limited himself to this form of evidence. 



