After making experiments concerning 50 infants under a perfect medical guidance, the following results were revealed by an investigation of the relation between their ingestion of "weaning food" and their bodily growth in the weaning period. (1) When the period before the beginning of weaning (about six months after birth) was compared with its completion time (about one year after birth), it was found that Kaup's index number rather rose at the completion time. (2) As to those infants whose Kaup's index number at the completion period of weaning became less than the index seen before the starting time, the amount and the percentage of calorie of milk taken daily are less than in the case of those infants whose index number became greater at the completion period than at the beginning. (3) The body-weight at the completion time of weaning seemed to have a close relation with the whole amount of calorie and protein daily taken by infants. (4) The body-weight at the completion time of weaning was still influenced by the weight at birth, but it was much slighter than before the start of weaning.