But it is not my purpose to discuss the question of the efficacy of removing adenoids and tonsils. The aim of this study is, rather, to determine experimentally whether or not there exists any causal relation between defect in this respect and lowering of intelligence level. One hears statements made both pro and con by physicians and laymen but there has been little experimental proof. It would seem to be rather useful for a physician to know in advance with how much probability of correctness he is speaking, when he advises a mother that the removal of adenoids and tonsils from the throat of her backward child will make him "bright." The question in the present case, however, is broader than that of relation between these afflictions and mental defect. We are inquiring not merely whether adenoids and tonsils are causes of sub normality or dullness, but also whether they tend to lower the intelligence quotient in general however high it may be. Would the mentally normal child with adenoids and tonsils have been superior without them, and would the superior child have been still more superior? What is the relation between adenoids and tonsils, and intelligence? The method employed in the present experiment would seem to give it value from the point of view of the clinical psychologist. With the present emphasis upon exactitude in mental testing, investigators have become interested in problem of the constancy of the I.Q. Adenoids and abnormal tonsils have been suggested as possible factors affecting this constancy. The results of the experiment should throw some light on the question. It should be understood that this study is concerned with general intelligence, and not with the child's efficiency as a member of society. The latter question is much broader than the one we are investigating. It includes not only intelligence, but physical state, emotional make-up, volition: in short, the personality as a whole. Success in school work for example, depends upon all of these factors. For that reason, the results to be reported here, cannot be interpreted as applying to this broader conception. We cannot say at the end whether or not the physical defects under consideration affect the child's success as a member of society. We hope to be able, however, to determine their effect upon one element of that success, namely intelligence.