II. CONFIGURATION OF THE CHEST

1. Various chest measurements have been made on 174 normal children ranging in age from newborn to 18 years and on 22 children with cystic fibrosis. 2. The patterns of growth of the anteroposterior (AP) and transthoracic (TT) and the sternal length (SL) in relation to height differ from that of the biacromial. After birth there is a rapid increase in the transthoracic and antero-posterior diameters, especially the former. Following this the growth of these two and the sternal length are relatively slow, accelerating again with increasing size. 3. The growth of a thoracic volume index (AP2.TT.SL) correlates well with the growth of the lung volumes in the ages where both are measurable. In younger children the growth pattern of the thoracic volume index is dissimilar to an extrapolation of the lung volume growth line. 4. Patients with cystic fibrosis have an increase in the antero-posterior and transverse diameters and to a lesser extent in the sternal length when compared with normal children of the same height. Because the transverse diameter is increased, a more sensitive indication of an abnormal chest is obtained from the AP diameter-height ratio than from the usual thoracic index (AP/TT).