The protein separated from human dental enamel by 2% HC1 and washing contains 12.1% N, 1.2% S, ash 8%, about 2% Ca, some fatty material and abundant tyrosine; cystine was not detected in it. It resembles horn and hoof in resistance to KCN, Na2S, Na thiolacetate, but differs from them in resisting subsequent exposure to trypsin. It also differs from the pseudokeratins descr. by Block and Vickery.