IN any survey of roentgenographic literature the surprising dearth of material dealing with technic for children will undoubtedly be noticed. Excellent instruction in adult technic may be given, but for child technic, if it is mentioned at all, the reader is offered some such vague direction as “halve the time of exposure for children.” The all-too-familiar result of an instruction of that kind is either the transparent-like negative or the densely dark one, neither of which is satisfactory for diagnostic purposes. This article is an attempt to contribute more definite technic within a limited field. The Iowa Child Welfare Research Station has been engaged in an x-ray program for the past twelve years. Its object has been to study, through this medium, growth and development of normal children from birth to maturity, correlating the results with findings through physical measurements. In anticipation of research projects along this line, the x-ray films have been limited to the bony structure of the body....