The woman {went} in the evening and the {doctor} gave {her} a small paper box tied {up} tight. "{It} is very heavy," {she} said. "May I {see} what it looks {like}?" "{No}," said the doctor, "{wait} until you get {home}." When she {got} home, and she and {her} husband {opened} the box so that he {could} take the first {dose} of medicine,--what do you think they {saw}? The box was {filled} with silver {money}. {This} was the {good} doctor's medicine. * * * * * =Importance of Mental Differences.= (1) _In school work._ One of the important results that come from a knowledge of the mental differences in children is that we are able to classify them better. When a child enters school he should be allowed to proceed through the course as fast as his development warrants. Some children can do an eight-year course in six years; others require ten years; still others can never do it. The great majority, of course, can do it in eight years. [Illustration: FIGURE XVIII--COMPLETION TEST--"DR. GOLDSMITH'S MEDICINE"] Norms for adults, as obtained from university students, are: TEST MEN WOMEN Substitution Test 29.1 32.2 Rote Memory, Concrete 28.5 28.6 Rote Memory, Abstract 28.4 27.9 Free Association 51.5 49.3 Completion, _Dr. Goldsmith's Medicine_ 48.1 49.0 Word Building 20.5 20.1 Logical Memory, _Costly Temper_ 64.0 69.6 [Illustration: FIGURE XIX--FREQUENCY SURFACES--COMPARING FOURTH GRADE WITH HIGH SCHOOL The numbers along the base represent mental age; those at the left, the number of pupils of the respective ages.] It may be thought that a child's success in school branches is a sufficient measure of his ability and that no special mental measurements are needed. This is a mistake. Many factors contribute to success in school work. Ability is only one of these factors, and should be specially and independently determined by suitable tests. Children may fail in school branches because of being poorly started or started at the wrong time, because of poor teaching, sickness, moving from one school to another, etc. On the other hand, children of poor ability may succeed at school because of much help at home. Therefore special mental tests will help in determining to what extent original mental ability is a factor in the success or failure of the different pupils.