564 THE POPULAR SCIENCE MONTHLY 



ment in lung capacity for girls about comes to a standstill or decreases 

 after 15 years of age; for boys the period is some time after 17 or 18. 

 Marked arrests in height and weight are uniformly accompanied by 

 arrest in growth of lung capacity. The boys and girls above and below 

 median height differ in their periods of accelerated growth in lung ca- 

 pacity in a manner similar to the differences in height and weight. 



In general it may be stated that there is more marked relationship 

 between disease or physical defects and growth in weight than growth 

 in height. Diseases seem to inhibit growth more during the late period 

 of childhood than earlier. Accelerated growth and resistance to disease 

 go hand in hand. The inception and removal of adenoid growth mate- 

 rially affect physical development. 



Selecting the individual growth curves of the girls whose physiolog- 

 ical changes have been recorded day by day during the periods of matu- 

 ration, it is evident that the taller girls mature early. 



Height and weight, therefore, offer excellent objective criteria for 

 teachers and parents for determining the advent of menstruation as a 

 factor in pubescent development and the onset of maturity. If the girl 

 is tall, healthy and well nourished, this physical stage may be reached 

 as early as 11 years in a normal girl; if tall, but underweight, it may 

 be delayed; if very short and markedly light, it may be delayed until 16 

 years of age. 



These conditions have wide educational application both in physical 

 training and school work. They emphasize the fact that the smaller 

 child should be treated as a younger individual, who has not the phys- 

 ical development and the accompanying mental disturbances and ex- 

 periences which would seem to be indicated by her chronological age in 

 years, and which, too often, has been used as a basis of classification, 

 training and social activities. 



It must be recognized, since we are investigating the school standing 

 or pedagogical age, and since promotions are based on marks, school 

 records must be taken at their face value, because they represent school 

 practise and because they offer tangible criteria of the efficiency of the 

 individual and of the school. 



If we accept progress through school when measured by marks, age 

 and grade distribution in highly specialized schools, as criteria of mental 

 development or at least indicative of nodes of mental maturation, we 

 have in this section of our discussion 135 individual pedagogical curves 

 based on 21,682 final term marks in the common school subjects, music 

 and deportment. The average school mark for the Horace Mann boys 

 is 81.9 per cent., for the girls 85.9 per cent., for the Francis W. Parker 

 boys it is 77.7 per cent., and for the girls, 80.9 per cent. 



Some of the main facts are : Girls maintain a higher school standing 

 than boys; there are also more repeaters among the boys; and fewer 



