Page:Popular Science Monthly Volume 85.djvu/568

564 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 capacity 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 materially affect physical development.

Selecting the individual growth curves of the girls whose physiological changes have been recorded day by day during the periods of maturation, 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 physical development and the accompanying mental disturbances and experiences 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