Fig. 2. Skeletal defects of the Raldh2^–/– forelimbs. (A) comparative view of the right forelimbs of control (left) and Raldh2^–/– embryos after four different conditions of RA supplementation (experimental group numbers as in Table 1). Note the progressive improvement of limb size and skeletal patterning according to the experimental group. (B) Skeletal pattern of a wild-type forelimb. (C-G) Examples of the Raldh2^–/– abnormal forelimb patterns. The embryos shown were from experimental groups 1 (C), 2 (D), 4 (E) and 5 (F,G). See Text for a full description of the skeletal patterns. In F and G, an arrowhead points the abnormally long and triphalangeal first digit (compare with B). h, humerus; r, radius; s, scapula; u, ulna; 1 and 5: digit number.