260 
IOWA ACADEMY OF SCIENCES 
of growth in children. If the absence of the thyroid gland will cause 
cessation in development is it not probable that disturbances in this 
gland's activity will cause lesser variations in growth? Periods of apathy 
or of nervous excitement in children; delayed dentition and belated 
ability to talk may mean a temporary disturbance in the gland function 
and not a less number of brain cells. 
Then too, the thyroid is but one of several ductless glands which 
we harbor in our anatomy and though speculation on the subject is as 
yet valueless, I am inclined to think that we may hope for much help in 
these subjects from the physiology of the future. 
XOTIS. 
I. Statistics kindly furnished me by the teachers of the Fairfield, 
Iowa, schools show: 
1. Children of the same class in the grammar school vary four years 
in age. 
2. More than three-fourths of each class are within one year of the 
average age. 
o. Nearly every class has but one or two individuals varying widely 
from the average age and usually in these exceptional cases the teacher 
is aware of a definite cause, such as the lack or the advantages in ear- 
lier training. 
4. In nearly all classes the average age for girls is less than that of 
boys; the average being seven and one-half months. 
II. In the most intelligent families of my home town, where the 
mothers have kindly furnished me data, the usual age for beginning 
the first dentition is from the sixth to the tenth month. Average ot 
those studied nine months. Walking is begun from the tenth to the 
thirteenth month; average 11.6 months, and the first word is spoken from 
at 8.5 to 12 months; average 10.5 months. 
In several instances an attack of sickness at the usual time for these 
events has delayed the development two or three months. In one in- 
stance a child spoke several words at ten months, then stopped speech 
altogether until eighteen months of age, when she began again to' learn 
to speak words. This was during apparent good health. 
