ON THE MENTAL AND PHYSICAL DEFECTS OF CHILDREN. 593 
ward, arranged in primary groups presenting only the class of defect indi- 
cated by the formula. To obtain the total number of cases with any class 
of defect, whether combined with other class of defect or not, the numbers 
representing all the primary groups containing such defect must be added . 
together. The total or compound group AB=primary AB+ABC+ ABD 
+ABCD. It is also possible, for the purposes of research, to arrange 
from the tables the children in whom any class of defect is absent, and 
thus compare their conditions in contrast with the children in whom such 
defects were present. Such actuarial work is useful in seeking the 
causation of defects. Examples have been worked out by Dr. Francis 
Warner.! 
This arrangement of our cases has afforded much information for the 
' solution of certain problems, and the means of answering many questions 
concerning conditions of childhood. It has become possible to compare 
similar groups of children under varied environment and at different ages. 
Comparison of the cases presenting some defect, as to their ages in 
relation to the standard in which they were placed, shows that 25-6 per 
_ cent. of the boys and 26:3 per cent. of the girls were over the average age 
recognised for the standard. Thus evidence is obtained of a lower mental 
status in children with the signs of defect, apart from the report of the 
teachers, while the value of the signs observed is indicated. Facts such 
as these can be arranged for any division of schools. 
It is well known that developmental and congenital defect forms an 
appreciable eause in the high rate of infant mortality, especially among 
males ; many children, however, with the lesser degrees of defect, survive 
to school age, and form 8°8 per cent. of the boys and 6°8 per cent. of the 
girls seen in schools. It was shown in our report of 1894 that conditions 
of defect are frequently associated in children ; the tables now published 
make it possible to show that such conditions vary in boys and in girls 
respectively in the age groups. 
Among the children with developmental defects, those who are seven 
years old and under have the lowest percentage association with additional 
or acquired defects. This is more marked among boys than girls. They 
have, however, a tendency to acquire nerve-disturbance, delicacy, and 
mental dulness under the continued action of their environment, as they 
grow older ; this is specially marked with the girls. When eight to ten 
years of age the proportion of those children who have acquired additional 
defects has risen 7 per cent. ; while at twelve years and older only 37 per 
cent. of the boys and 25 per cent. of the girls with developmental defects 
are free from additional or acquired delicacy, nerve-disturbance, or mental 
dulness. Further, among developmental defect cases, the signs of nerve- 
disturbance are more associated with other defect in boys under eleven 
years ; while at all ages the association with low nutrition and mental 
dulness is greater in girls. At eleven years of age and over, develop- 
mental defect is most associated with nerve-disturbance, delicacy, and 
dulness in the girls. 
The calculations upon which these statements are made, as founded 
upon the tables here given, will be found in the ‘Statistical Journal,’ 
March 1896. 
Brain-disorderliness, as indicated by abnormal nerve-signs, is a more 
potent cause of mental dulness than congenital defect of development of 
1 See Statistical Journal, March 1896. 
1896, QQ 
