Introduction
The observations to be described were designed to provide a Presidential Address to be presented before the Society for Pediatric Research. Retirement or graduation from this Society occurs at an interesting developmental age, and one of the privileges of the President is to set forth before the Society some of the thoughts that, at the delicate age of 45, he believes are important. Granted this purpose of his address, the selection of a topic tends to provoke deep introspection concerning the relative importance of his many cherished concepts, a challenge I have met by worrying almost to distraction not only my wife but also many good friends who were forced to concur in the decision of the moment.The results of these observations indicate that the interpretation of many data on physiological and biochemical growth of young infants has been subject to two preconceptions of questionable value. These are: