Schweitzer et al. (1999) subjected these filaments to microscopic, morphological, mass spectrometric, and immunohistochemical studies and found that they consisted of beta-keratin, which is the primary protein in feathers.
Schweitzer et al. (1999.) su podvrgli te strukture mikroskopskim, morfološkim, spektrometrijskim i imunokemijskim istraživanjima, te otkrili da se sastoje od beta-keratina, preovladavajućeg proteina u perju.