EFFECT OF BILATERAL STRUCTURE ON KERATIN FIBERS 36l stained by both acid and basic dyes and that the phenomenon is to be associated with the greater reactivity or accessibility of the orthocortex to chemical reagents rather than to differences in the number of sites for dyeing in the two portions of the wool fiber cortex. Such a finding is also consistent with the fact that all keratin fibers, regardless of their origin, exhibit about the same acid-combining capacity. Another point raised by this finding that the orthocortex is preferentially stained by both acid and basic dyes is its possible relationship to objections raised by Harris (6) in respect to the amino acid analyses of Golden, Whitwell and Mercer (5). The paracortex-plus-epicuticle fractions analyzed by Golden et al., were prepared by the previously described process of supercontraction followed by enzymatic digestion by microscopic observation this process appeared to extract thl•eorthocortex cleanly, leaving behind a paracortex-plus-epicu- ticle fraction. Harris has pointed out that, if this preparative procedure were to extract residues preferentially from the paracortex containing lower amounts of cystine and of basic amino acids such as arginine, the remaining paracortex would contain artificially high amounts of cystine and basic amino acids. At present no direct method has been used to determine the cystine contents of the two portions of the wool fiber cortex. The cystine differences observed, however, are large and in general are in accord with the cystine contents found by a direct method for other keratin fibers that are primarily "ortho" or "para" in nature. These are discussed later in this paper. No such indirect confirmation of the amino acid analyses is avail- able for the observation of the excess of basic amino acids in the para- cortex. The confirmation given to this observation by the differential dyeing results of Ohara and of Horio and Kondo appears now to be spurious. In fact, a recent study of the amino acid composition of •-ACTH (a physiologically active component of corticotropin from hog anterior pituitary) by Bell and others of the American Cyanamid Company (1) indicates a basis for the objections of Harris. They found this protein (molecular weight 4566) to consist of 39 amino acid "toohomers," of which 16 were different, to have its acidic and basic amino acid components grouped more or less separately from one another along the molecule, and to have its acidic amino acid components preferentially extracted when treated with enzymes. To the extent that an analogy may be drawn between the work of Golden et al. (5), and these findings, that enzymes can extract dicarboxylic amino acids from a complex protein under some circumstances, any assumptions made regarding the absence of such extraction may be incorrect. Still another indication of ortho-para differentiation in wool fibers is observed when a wool fiber is first subjected to acid and then exposed to alkali (3). A digression is in order at this point. In connection with the wool research programs at Textile Research Institute, an investigation

362 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS was made of the relationship between a chemical test for damage to the wool fiber (such as the classic alkali-solubility test) and physical tests for 6O 5O 4O 50 20 15 ',% o H•SO 4 • [] H2S04 followed by HCHO A HCHO followed by H2SO 4 I • I • I I I I I • I 4 8 12 16 20 24 TIME OF EXPOSURE TO AOID (HOURS) Figure $.--Alkali insolubility of yarns from fabrics boiled in sulfuric acid solution for varying times. damage (such as measurement of the force-extension properties of fibers from degraded wool fabric samples). It was also of interest to learn, if possible, what bearing the ortho-para structure might have on the alkali-