In bell stage(E19),the positive staining was detected in both inner and outer enamel epithelium,but the inner was less than that of the outer and less positive staining was also found in the cells of stratum intermedium and stellate reticulum.

• 钟状期(胚胎19d),内、外釉上皮阳性表达,但内釉上皮较外釉上皮表达弱,中间层及星网状层细胞弱阳性表达;