Clearing and Staining of Embryos for Demonstrating Ossification

The authors have outlined their method for demonstrating fetal ossification whereby the tiniest bones may be studied in their relation to the rest of the skeleton without destroying the specimen. In general the method is that devised by Schultze for clearing the soft tissues with potassium hydroxide. The authors then stain the skeletal system by immersion of the entire specimen in a 0.1% alkalinized aqueous solution of alizarin red S. The dye is removed from the soft parts by decolorization in alcohol-glycerin baths. Details are given for the preparation of the fresh fetus, fixation in alcohol or formalin, clearing, staining, decolorizing, mounting and preservation.