374 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS connective function. On the skin of these people, a complete disorganization (14) therefore becmnes apparent, in which each component--hair germ, hair follicle, sweat gland, sebaceous gland, covering epithelium, melanocytes, and blood vessels--separately begin to display limited growth, and finally again adjust themselves to one another but to a limited extent. INDIVIDUAL DIFFERENCES These differences manifest themselves in the type of skin--dry, greasy and normal. Analogous to medico-psychological typology, we might also speak of an asthenic and pycnic skin. The asthenic skin grows and recovers slowly and the activity of the adnexa is slight. Because of a typical peculi- arity the keratinization process (15) does not proceed in the normal way. Fish-like scales are formed to which the disease owes its name of ichthyosis. The metabolic disturbance in the keratinization process may be congenital or acquired. It is very interesting that a syndrome corresponding comple- tely with ichthyosis vulgaris can be encountered in some test subjects with a normal skin, to which triparanol (a substance which blocks the synthesis of plasmacholesterol in the liver) has been administered. Ichthyotic skin may also develop in the course of serious general diseases. The opposite of this, the thick, rapidly growing skin, is known in its most extreme form as ichthyosis congenita. The common seborrhoeic skin is formed functionally in puberty under influence of androgenic hormones, but nevertheless is very probably engendered in these people in their young years. DIFFERENCES BETWEEN THE SEXES Although many psychologists would like to see the difference between the sexes ascribed purely to cultural causes (a farmer's wife is a farmer who bears children), for the dermatologist there are striking differences, even though these are most pronounced at the time of sexual maturity, and in old age not only the hair coverage tends to be similar for both sexes. There is also a distinct difference in peripheral blood flow, which in women, at least in the Netherlands, is considerably more limited than in the male. This also applies to sweat secretion. SEASONS By and large it is possible to differentiate "summer" and "winter" skin. In this way the fully functioning, rapidly growing, profusely sweating and metabolically active summer skin--fully supplied with blood--is contrasted with the non-sweating, inactive winter skin, only poorly supplied with blood. The effect on the stratum corneum of a summer skin, is swelling and possible plugging of the sweat gland pores. The effect on winter skin is drying out and hardening followed by chapping and eczematic symptoms.

THE VARIABILITY OF THE SKIN 375 Moreover "natural skin cream" may crystallize when exposed to low temperatures. Corresponding to this is an inactivity of the cellular com- ponents of the epidermis, which in my opinion makes it probable that, on the one hand, this skin is not readily capable of spontaneous recovery, and will react in an unexpected way to the local application of ointments, but, on the other hand, does not easily react with exanthema on internal noxa. CONCLUSION It is hoped that the foregoing has presented a general idea of the great variability of the skin. As the anatomical and physiological investigation of the skin is directed more and more to quantitative aspects it will become possible to analyze more accurately than now, the effects of cosmetics under various circumstances, in various individuals, on different paris of the human skin. (Received: 7th February 196•t.) REFERENCES (1) A. G. Matoltsy, Z. Schragger and M. N. Matoltsy, J. invest. Dermatol. 38 251 (1962). (2) H. Pfleiderer Z. exptl. g/led. 90 24S (1933). (3) J. W. H. Malt Dermatologica 104 19 (19S2). (4) R. K. Winkelman, S. R. Scheen, R. A. Pyka and M. B. Coventry in W. Montagna and R. A. Ellis Advances in biology of skin Vol. II--Bloodvessels and circulation 1 (1961) (Pergamon Press Ltd., Oxford). {5) R. H. Fox and O. G. Edholm ,Brit. Med. ,Bull. 19 110 (1962). (6) T. Bedford J. Hyg. 35 307 (1935). (7) A. C. Burton and G. Froese J. Appl. l•hysiol. 10 235 (1957). (8) J. R. DePalma, S. R. M. Reynolds and F. I. Foster Am. Heart J. 23 377 (1942). (9) H. Pinkus Dermatologica 117 369 (1958). (10) J. W. H. Malt Ned. Tijdschr. Geneesk. 107 2017 (1963). (11) P. V. Marcussen J. Invest. Dermatol. ,10 263 (1963). {12) J. S. Strauss, A.M. Kligman and P. E. Pochi J. Invest. Dermatol. 39 139 (1962). .(13) N. N. Epstein in R. B. Rees Dermatoses due to environmental and physical factors 37 (1962) (Ch. C. Thomas, Springfield). (14) D. TXV. Smithers Lancet i 493 (1962). (15) G. Swanbeck Acta Dermato-Venerol. 39 Suppl. 43 1 (1959).