36 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS non-keratin constituents also takes place. In differentiating epidermal cells, cytoplasmic fibrillation does not seem to be a gradual process and the fibrils never seem to reach concentrations as high as in differentiating cells of the hair cortex. Elimination of nuclear and cytoplasmic non-keratin components is also less perfect. Differences can be recognised in the chemical composition of the keratin which is formed in both hair cortex and in the epidermis. , While hair keratin contains the basic amino acids: histidine• lsyine and arginine in a character- istic ratio of 1: 3: 10, this ratio is absent in epidermal keratin. The other amino acids also occur in differing quantities. ,It would appear that either the availability of amino acids might be different in the hair follicle and the epidermis, or that keratin synthesis proceeds according to different principles in these keratinising tissues. , "THE BIOSYNTHESIS OF FIBRES" E. H. Mv-RC•R The formation of many fibrous systems follows the following course: primary synthesis of a non-fibrous macromolecular precursor, the trausforma- tion of the precursor into a fibrous modification, the arrangement of these protofibrils into more organised structures and, in some cases, the hardening or tanning of the final formation. Thin sections of a selection of fibre-forming cells, including silk-forming cells of the silkworm, collagen-forming fibroblasts of the skin of the mr, the cells forming the egg case of the cockroach, certain chitin-forming .cells of insects, and mammalian epidermal cells, lead to the following tentative con- clusions: protein fibre formation is associated with the presence of dense ribonucleoprotein (RNP) particles, as is also the case with cells forming soluble proteins chitin-forming cells have few dense RNP particles if the fibre-precursor is to be secreted from the cell the RNP particles are associate•d with reticulum if the protein fibrils merely accumulate within the cells the RNP particles lie in clusters freely in the cytoplasm. The secretion of the protein precursor may be effected through long, thin, finger-like protrusions of the cell membrane or, if synthesis is very rapid, large accumulations may separate in lumps at the cell edge. The transformation of the non-fibrous precursor into protofibrils seems most often to be a kind of aggregation into linear or helical aggregates in which the original structure of the macromolecule is preserved. These protofibrils often separate spontaneously in vitro and may be photographed. The organisation of protofibrils into parallel arrays, networks, membranes, etc., is due to some added control mechanism, such as shear due to flow or the presence of already organised material. Keratin protofibrils form spon- taneously and in hair seem to owe their orientation to a slight initial flow

ABSTRACTS OF PAPERS ON THE BIOLOGY OF HAIR GROWTH 37 in the deformed cells this controls the direction of fibrils subsequently added. "THE NATURE OF HAIR PIGMENT" TttOM•S B. FITZPATRICK, PETER BRUNET AND ATSUSttI KUKITA Dept. of Derrnatology, University of Oregon, Portland, Oregon. The large variety of hair pigments has provided material on which naturalists, geneticists,, and biochemists have been able to carry out com- parative studies on the r, ature and control of pigmentation. Although superficial examination of hair would indicate a wide range of colour hues, microsqopic examination has re•ealed ,only three types of pigmented granules, namely, black, brown and yellow. , The study of the nature of hair pigment has proved generally unrewarding because it has not yet been possible to isolate pure fractions for chemical characterisation. Many of the advances on the nature of hair pigment have been made using the synthetic approach following the action of enzymes in the hair bulb on chromogenic substrates. But ultimately it xvill be nece'•ary to combine such a synthetic approach with chemical analysis of naturally occurring pigment. Differences in hair colour are biochemical differences and the genetic pattern of hair colour indicates that brown and black pigment is under the same genetic control, whereas, yellow (Pheomelanin) is under a different genetic control. Thus, two separate, but possibly interrelated, metabolic pathways of brown-black and yellow hair pigment are suggested. , Using a histochemical radioautographic technique and dl-tyrosine-2-C •4 as a substrate, it has been shown that the hair bulbs of mice incorporate tyrosine into pigment cells. The activity of tyrosinase is related to the stage of the hair cycle. In the C-57 black mouse, tyrosinase activity is not detect- able with the radioautographic technique during Anagen I and II, but appears weakly in Anagen iii and gradually increases in amount during Anagen IV, V and VI. Tyrosinase activity is absent during the Telogen stage of the hair cycle. The factors that regulate •the tyrosinase activity during the hair growth cycle are not known. It is possible, as suggested by Chase, that the cessation of tyrosinase activity iust prior to catagen may be related to the development of an inhibitor. The degree of incorporation of tyrosine-2-C •4 indicated by silver deposit in the radioautographs is very strong in intense brown mice (a/a b/b C/C D/D P/P) and in brown mice with Maltese dilution where d/d replaces D/D.' There is slightly less incorporation in both yellow mice (AY/• B/B C/C D/D P/P) and intense blacks (a/a B/B , C/C D/D P/P) and decreased but detectable incorporation in black mice with pink-eyed dilution, p/p replacing P/P of the intense blacks. Albinos showed