During the same year, another examination along the same lines was conducted in the William McKinley Primary School,[8] where a large number of dull children had been grouped in special classes.
None of these children were mentally defective, says Dr. Cornell, and only a few were really backward. The proportion of physical defect was found to be very large,—in 174 pupils, 188 physical defects (68 eye-strain, 40 nasal obstruction, 80 miscellaneous, 11 hypertrophied tonsils.) In a special class at the Wharton school, numbering 22 children, 14 of the children suffered from adenoids, associated in 3 cases with enlarged tonsils. Since no comparison is made with normal classes, this survey cannot be regarded as conclusive.
Wallin, in his book, "Mental Health of the School Child," discusses several other investigations of the relation of intelligence to physical defect. Only those studies in which were included adenoids and tonsil conditions will be reviewed here. Those by Ayres and Cornell have been described above.
In Elmira, New York, says Wallin, "an investigation of repeaters in the second grade showed that 21 per cent of those who required three years and 40 per cent of those who required four years to complete the grade had adenoids, as against only 19 per cent of those who required only two years to do the grade."
Another study described by Dr. Wallin was made by Heilman in 1907 of 1000 Camden repeaters. The correlation between pedagogical retardation and percentage of defect in each group was as follows:
| Defects | Retardation | ||||
| 1 yr. | 2 yr. | 3 yr. | 4 yr. | 5 yr. | |
| Per Cent | |||||
| Health | 16·5 | 21·3 | 28·0 | 19·0 | 37·5 |
| Nutrition | 13·4 | 8·9 | 17·2 | 20·2 | 17·5 |
| Adenoids | 6·2 | 7·3 | 8·1 | 9·6 | 7·5 |
| Speech | 5·2 | 5·1 | 4·2 | 10·5 | 20·0 |
| Visual defects | 15·5 | 15·9 | 18·2 | 22·8 | 22·8 |
| Auditory | 8·2 | 6·7 | 4·9 | 6·1 | 10·0 |
Burpitt[9] describes an investigation of 400 children, 200 male and 200 female, considered by their teachers to be "dull and backward, but not to fall within the meaning of feeble-mindedness as given in the Mental Deficiency Act of 1913." The children were examined for physical defects and other abnormal conditions. The author says that in 36 per cent of the cases, the cause for backwardness was found to be "inherent dullness." (The basis for judgment of inherent dullness is not given.) Adenoids and tonsillar tissue were found in 18·75 per cent of the cases, and were "more prevalent than among the children of the area as a whole."
The degree of retardation, based upon the number of school standards below normal, was ascertained for pupils who suffered from various defects. The relative retardation was expressed by the fraction n/(A-5) where n = number of years retarded, and A = age. Eighteen per cent of the children were so retarded that the fraction was greater than 3-9. These were divided into two groups,—3-9 to 4-9 and 4-9 to 5-9. The results are given in the following table:
| Causes | 46 children 3-9 to 4-9 | 24 children 4-9 to 5-9 |
| Inherent dullness only | 8 | 3 |
| Inherent dullness and one or more physical defects | 7 | 2 |
| Irregular attendance with one or more physical defects | 9 | 6 |
| Irregular attendance | 2 | 3 |
| Adenoids only | 2 | 0 |
Turning to what the author calls single causes,—present in 170 cases out of the 400,—