122 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The pore size of the membranes in the blood vessel walls as well as in the epidermis (50) may be smaller than the molecular volume of the sub- stances. For instance, a pore diameter of 55 ,•.. will retain egg albumin (51). Hydrostatic pressure may also affect the passage (52). In other aspects of persorption it has been found recently that the skin color may be controlled by topical application of certain chemicals. The monobenzyl ether of hydroquinone inhibits the oxidation of tyrosine so that melanin formation may be prevented (53). On the other hand, white skin patches of vitiligo may be made darker by using 8-methoxypsoralen along with sunlight. This chemical stimulates tyrosinase activity in the cells of the lower layers of the epidermis (54). This suggests the study of enzymes in the skin which may possibly influence persorption. Acid phosphatase has been found in regions of keratin transition (55). Esterases have been reported in high concentration near the surface (56). Succinic dehydrogen- ase (57) and cytochrome oxidase have also been observed (58). Mon- amine oxidase may be responsible for the ammonia from sweat glands (59). Various aspects of this phase offer a wide field for future research work. Age offers many problems in persorption (60). For instance, estrogenic ointments have been recorded to have a beneficial effect (61) on senile skin though a visible improvement has been questioned in one instance (62). There is some question as to whether the collagenous and elastic tissues change markedly with older age thus affecting persorption (63). Aging of protein, ground substance, hyaluronic acid, hyaluronidase, glycogen and other constituents must be further investigated (64). Observation of cir- culatory changes of both blood and lymph in the dermis along with oxida- tion studies will be of value in considering persorptive measures (65). The scalp (66) should be considered specifically, for it has peculiarities not found in other parts of the skin. Since aging of skin does not necessarily correspond to chronological aging other factors such as skin exposure, nutrition (67), sensitivity and possibly stress (68) should be investigated. Poison ivy (69) and other similar skin reactions are only partly understood with respect to skin penetration and present many research problems. The action of lysergic acid diethylamide (70) on capillary resistance introduces serotonin inhibition for study. Cor- tisone and its derivatives may suppress vascularization through action on the ground substance and hyaluronic acid (71). Temperature, humidity, season and sex also probably contribute to differences in persorption (72). Skin-fold thickness measurements (73) may prove useful to predict persorp- tion values. SUMMARY Due to considerable discussion of terminology for the passage of materials through the skin, a new term '•Persorption" has been proposed. Different

PERSORPTION 123 degrees of persorption have been discussed, and various methods of deter- mining persorption have been reviewed. Many factors such as fat and water solubility, contact with the skin, environmental conditions, intact- ness, thickness and age of skin, and circulation of blood and lymph all need much additional research work to evaluate their effect on "Persorption." REFERENCES (1) Dawson, W. T.,/Inn. Internal Med., 1:3, 1594 (1940). (2) Armstrong, G. E., Shaeffer, J. R., and Artz, C. P., U.S. ,4rmed Forces Med. St., 7, 320 (1956). (3) Leider, M., and Bunche, C. M., virch. Dermatol. and SyphiloL, 69, 563 (1954). (4) Drug and Cosmetic Ind., 77, 259 (1955). (5) Giroud, A., and Leblond, C. P., vinn. N.Y. vicad. Sci., 53, 613 (1951). Leblond, C. P., and Walker, B. E., PhysioL Revs., 36, 255 (1956). (6) Suskind, R. R., Ind. Med. and Surg., 24, 413 (1955). Lubowe, I. I., J. So½. COSMETro CHEM., 6, 19 (1955). Bateman, F. J. A., Brit. Med. 7., 554 (March 10, 1956). Schwartz, L., "The Prevention of Occupational Skin Diseases," New York, McGraw-Hill Book Co., Inc. (1955). (7) Benjamin, F. B., •7. Invest. DermatoL, 26, 471 (1956). (8) Rothman, S., Trans. N.Y. vicad. Sci., Sec. H, 12, 27 (1949). Seeberg, V. P., Hildago, J., Wilken, W., BenJams, H. N., and Lundblad, J., 7. vim. Pharm. vissoc., Sci. Ed., 45, 342 (1956). Oster, K. A., and Golden, M. J., Trans. N.Y. vicad. Sci., Sec. H, 12, 132 (1950). Barlow, A. J. E., and Chattaway, F. W., Lancet, 269, 1269 (1955). Stoughton, R. B., and Novak, N., •7- Invest. DermatoL, 26, 127 (1956). (9) Montagna, W., "The Structure and Function of Skin," New York, Academic Press (1956). Behrman, H. T., "The Scalp in Health and Disease," St. Louis, C. ¾. Mosby Co. (1952). Kalish, J.,"Skin Research." In each monthly issue of Dvug and Cosmetic Ind., starting with Vol. 76, 393 (1955). Carruthers, C., and Suntzeff, V., Physiol. Revs., 33, 229 (1953). Kooij, R., Dermatologica, 112, 62 (1956). Pillsbury, D. M., Shelley, W. B., and Kligman, A.M., "Dermatologv," Philadelphia, W. B. Saunders Company (1956). Pillsbury, D. M., vinn. Rev. Physiol., 2, 151 (1940). Kalish, J., Drug and Cos- meticind., 76, 622 (1955). Flesch, P., J. Soc. COS•aEX•C C•E•a., 6, 14 (1955). (10) Rothman, S., 7. Lab. and C/in. Med., 28, 1305 (1943). Rothman, S., J. Soc. Cos•aE•rxc CaEca., 6, 193 (1955). Rothman, S., "Physiology and Biochemistry of the Skin," Chicago, The Univ. of Chicago Press (1954), Calvery, H. O., Draize, J. H., and Laug, E. P., Physiol. Revs., 26, 495 (1946). Treherne, J. E., 7- Physiol., 133, 171 (1956). Peck, S. M., Drug and Cosmetic Ind., 72, 46 (1953). Hadgraft, J. W., and Somers, G. F., 5 e. Pharm. andPharmacol.,8, 625 (1956). Gulllot, C. F., and Valette, G., Technique Pharmaceutique, 1, No. 9 (1954). (11) Newburgh, L. H., and Johnston, M. W., Physiol. Revs., 22, 1 (1942). Blank,I.H.,Drug and CosmeticInd., 76, 758 (1955). 12) Peiss, C. N., Randall, W. C., and Hertzman, A. B., 5 e. Invest. Dermato!., 26, 459 (1956). 13) Woodbury, D. M., vim. 7. Physiol., 185,281 (1956). (14) O'Brien, J.P., 5 e. Invest. Dermatol., 15, 95 (1950). Montagna, W., Chase, H. B., and Lobitz, W. C., Ibid., 20, 415 (1953). (15) Shelley, W. B., and I,evy, E. J.,Ibid., 25, 249 (1956). (16) McConnell, W. E., Chem. Products, 11, 391 (1955). Florestano, H. J., Bahlet, M. E., and Jeffries, S. F., 5 t. vim. Pharm. vissoc., Sci. Ed., 45, 538 (1956). Lesser, M. A., Drug and Cosmetic Ind., 73, 764 (1953). Hilfer, H., Ibid., 77, 41 (1955). Kalz, F., and Scott, A., virch. De•matol., 73, 355 (1956). Collins, A. P., and Zopf, L. C., vim. Prof. Pha:'macist, 22, 691 (1956). Mutimer, M. N., Riffkin, C., Hill, J. A., Glickman, M. E., and Cyr, G. N., 5 t. vim. Pharm. vissoc., Sci. Ed., 45, 212 (1956). Perlman, H. H., and Leuallen, E. E., 5 t. Pediat., 43, 578 (1953). (17) Jacobi, O., and Heinrich, H., Drug and Cosmetic Ind., 75, 34 (1954). Lubowe, I. I., Ibid., 77, 43 (1955). Kvorning, S. A., victa Pharmacol. et. ToxicoL, 6, 13 (1950). Kvorn- ing, S. A., and Svendsen, I. B., 5 t. Invest. Dermatol., 26, 421 (1956). Frazier, C. N., and Blank, I. H., "A Formulary for External Therapy of the Skin," Springfield, Ill., Charles C Thomas (1954). Martin-Scott, I., and Ramsay, A. G., Brit. Med. 7., 1525 (June 30, 1956). Brain, R. T., Ibid., 299 (Aug. 4, 1956). (18) Bucks, J. W., Jr., 5 t. Louisiana Med. Soc., 107, 29 (1955). Grady, E. D., U.S. virmed Forces Med..7., 7, 1471 (1956).