752 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS their absence during telogen (55, 56), may reflect an underlying intrapapilla synthetic cycle, determined during papilla development, which is causally related to subsequent changes in the epidermal component. (It may be relevant here that feather development in culture was suppressed on in- hibition of alkaline phosphatases (57)). Similarly, observations on the various geometrical correlations which exist between the dermal papilla, the matrix of the hair bulb, and the characteristics of the hair grown from a follicle have invited speculation that the papilla may be exercising ultimate control in some unknown way (58-60). Papilla/matrix interactions would also seem to be involved in the "cellular shunt" system which operates to produce complementary thicken- ing of the Huxley layer of the inner root sheath in follicles producing hairs of varying cross-sectional shapes and sizes (61-63). The reduplication of the basal lamella within the bulb, as observed in follicles of man (64) and the guinea pig (65), may also in some manner relate to papilla/matrix inter- actions. Finally it must not be forgotten that the dermal papilla is structurally confluent with the dermal sheath with which it develops during ontogeny. This sheath is presumably involved both in the vertical integration of the follicle (29) and its maintenance. It was seen to be the source of papillae, where they regenerated, and may have played a role in the preservation of the superficial region of the whisker follicles which did not regenerate papillae. It is also possible that inductive stimuli from the dermal sheath, perhaps involving the glassy membrane, help establish and maintain that peculiar follicular epidermal variant, the outer root sheath. Certainly it is likely that the dermal component of the follicle, by virtue of an overriding specific influence, resists the known influence of the extrafollicular dermis in controlling the behaviour of adjacent epidermal cells. These and other interactive considerations are discussed by Straile (46), Cohen (44), and Oliver (66). (Received.' 24th February 1971) REFERENCES (1) Montagna, W. and Van Scott, E. J. in Montagna, W. and Ellis, R. A. The biology of hair growth 39 (1958) (Academic Press, New York). (2) Straile, W. E., Chase, H. B. and Arsenault, C. T. Growth and differentiation of hair follicles between periods of activity and quiescence. J. Exptl. Zool. 148 205 (1961). (3) Chase, H. B. in Lyne, A. G. and Short, B. F. Biology of the skin and hair growth 461 (1965) (Angus and Robertson, Sydney). (4) Hardy, M. H. The development of pelage hairs and vibrissae from skin in tissue culture. Ann. N.Y. Acad. Sci. 53 546 (1951). (5) Pinkus, H. in Montagna, W. and Ellis, R. A. The biology of hair growth 1 (1958) (Academic Press, New York).

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