272 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS extract. The fact that more extractives were found in the "pounded" callus sample is not surprising, since different lots of callus are involved. The moisture absorbed by these extracts is shown in Table 7. Qualitative tests performed on these extracts indicated the presence of appreciable quantities of amino acids, polypeptides, urea and ammonium salts and of small quantities of lactates (28), penroses (29) and mucopolysaccharides (30). A comparison of the moisture absorbed by different lots of washed and unwashed callus is shown in the curves plotted in Fig. 3. The curves show 25 •,/.,•o Lot 4 (milled) Lot 2WW (pounded) Lot 2 (pounded) •!"/•'i.x Lot 4WW (milled) i I ,...' ß ... Lot •SW ////,.,..... •,•/ Lot 3WW(milled) 40 50 60 70 80 90 I00 Relative Humidity (%) Figure &--The water sorption at equilibrium of pulverized, washed and unwashed callus at dif- ferent R.H.'s at 23øC. •: 2øC. that the water absorption of washed and unwashed callus is almost the same at 45 per cent and 60 per cent R.H. but that differences exist at 90 per cent R.H., depending on the lot of callus. Thus, washed and dried pul- verized callus (Lot #2 ww) absorbed no more water than a similarly pul- verized unwashed callus (Lot #2), regardless of the humidity conditions during storage. On the other hand, washed pulverized callus (Lot #4 ww) absorbed approximately 13 per cent less water at 90 per cent R.H. than the unwashed callus. In another lot (Lot #3 ww), the water sorption of water- washed callus was almost identical with that of solvent and water-washed callus (Lot #3 sw). It appears that the presence of the water-soluble con- stituents may enhance the water sorption of callus at 90 per cent R.H. in

WATER HOLDING CAPACITY OF CALLUS 273 some cases. However, enhancement of this type is not observable at lower R.H.'s (60 per cent or less). D. lt/ater Sorption of Substances I4/hich Occur Naturally in Skin and Their Effect on Callus Spier and Pascher (4-9), Szakall, et al. (12, 13), Flesch and Esoda (31), Dowling and Naylor (32), Roe, et al. (33), Matoltsy and Balsamo (34, 35) and Bolliger and Gross (36) have studied the composition of the water- soluble fraction of back scrapings, callus, skin strippings and scalp flakes. While in most instances these inves- TABLE 7--WAwv. Sov. vvso• or WAVEU SOLUBLE CALLUS EXTP. AeTS AT 60% R.H. A'r 23 ø m 2øC. Extract Derived from Water Absorbed, % Pounded callus (from Lot #2 23.2 ww + 5 ww combined) Wiley milled--water extracted 23.3 (from Lot #3 ww) Wiley Milled--solvent/water 22.0 extracted (from Lot #3 sw) TABLE 8--MoIsTURE SORPTION OF SELEOTED "NAvt•aAL" CALLt'S COMPONENTS AT 60% R.H. aT 23 ø + 2øC. Component Moisture Sorption at Equilibrium, %. Amino acidst 19.5 Sodium lactate 66.0 Urea nil Sodium chloride nil Polypeptides:• 18.3 Mucopolysaccharide:f 1 l. 2 Glycerol 33.8 Propylene glycol 31.9 * Average of two samples, calculated on dry weight of material. t Hy-Case, casein hydrolysate, Sheffield Chemical Co. $ Polypeptide 37, partial leather hydrol- ysate, Maywood Div., Stepan Chemical Co. •f Gastric Mucin. tigators did not attempt to make a complete analysis, there is good qualitative agreement concerning the nature of the bulk of the water- soluble components (section C above). The major constituents include amino acids, factares, urea, inorganic salts and water-soluble polypeptides, and their ability to absorb moisture seems to have con- siderable practicalimportance. Al- though penroses, hexoses, hexos- amines, mucopolysaccharides, uric acid, creatinine, guanine, purines, citrates and formates were also iden- tified, their concentration appears to be too low to have an appreciable effect on moisture absorption. It seemed of considerable interest to evaluate the hygroscopicity of these materials. It seemed still more im- portant to determine whether the addition of one of these naturally occurring substances could alter the water sorption of washed callus. Samples of mixed amino acids,* sodium lactate, urea, sodium chloride water-soluble polypeptides,t and gastric mucin (representing a muco- polysaccharide) were dried to constant weight in a vacuum desiccator at room temperature over P20•. These materials were then stored in a constant relative humidity chamber at 60 per cent R.H. at room tem- perature until they reached constant weight. * Hycase, a casein hydrolysate, Sheffield Chemical Co. t Polypeptide 37, a leather hydrolysate, Maywood Div., Stepan Chemical Co.