QUANTITATIVE MICROSCOPY 507 be obtained by comparing the above secured values with those obtained in the same manner from preparations of different compositions or made by other manufacturers. A set of well-secured relative values can easily be connected to an absolute scale by one single calibration which, as a routine method, may be too difficult and time consuming to carry out. In the search for improved methods of observation and for indicating parameters, a surprising wealth o. information and techniques can be found in the literature, and often in the specialized literature published in totally unrelated fields. More often than not, such special techniques lend them- selves to easy adaptations. Very often, indicating parameters used in these fields of research can be applied to the cosmetic problem under study then it is especially advisable to use these known parameters. Their behavior, sensitivities to errors or changes, and range of validity have often been studied and described. Frequently, one will find all of the mathematics, which also apply to one's own problems, already developed. Cosmetic research with its highly diversified problems and demands for specialized knowledge seems to require even more imagination than research in any one particular field. Anybody actively engaged in research in this field will have to take advantage of every analytical method that might possibly be useful to him. Among these, quantitative microscopy plays an important role. (Received December 17, 1963) REFERENCES (1) T. Caspersson, Cell Growth and Cell Function, W. W. Norton and Co., lnc., New York 1950. (2) G. Oster and A. W. Pollister, Physical Techniques in Biological Research, Academic Press, Inc., New York, 1955. (3) M. L. Mendelsohn, 7. Bio•hys. Biochem. Cytol., 4, 407 (1958). (4) Rinne-Berek, in C. H. Claussen, A. Driesen and S. R6sch, .4nleitunge,l zu optischen Untersuchungen reit dem Polarisations-mikroskop, E. Schweizerbart, Stuttgart, 1953. (5) H. Ehrenberg, in H. Freund, Handbuch der Mikroskopie i,i der Technik, Vol. l, Part 2, Umschau-Verlag, Frankfurt, 1960, pp. 2- 186. (6) A. H. Bennet, H. Jupnik, H. Osterberg, and O. \¾. Richards, Trans. rim. Microscop. Soc., 65, 99 (1946). (7) H. Wolter, Schlieren, Phasenkontrast- u•d Lichtschnittverfahren, in S. Fliigge. Encyclo- pedia of Physics, Vol. XXIV, Springer-Verlag, Berlin, 1956, pp. 555-645. (8) E. Schuchardt, Das Integrationsverfahren in der mikroskopischen Tec•nik, in H. Freund, Handbuch der Mikroskopie in der Tech•ik, Vol. I, Part 1, Umschau-Verlag, Frankfurt, 1957, pp. 564-588. (.9) D. Hoenes, Mikroskopische Gru•dlage• der Technischen Gesteinskunde, in H. Freund, Handbuch der Mikroskopie in der Technik, Vol. IV, Part 1, Urnschau-Verlag, Frankfurt, 1955, pp. 362-378. (10) A. Thaer, Staub, 38, 555 (1954). Idem, Gliickauf, 91, 29 (1955). (11) J. Juda, K. Medenbach, Z. wiss. Mikroskop., 64, 218 (1959). (12) H. Osterberg and A. J. Carlan, Trans. •tm. Microscop. Soc., 77, 340, 353 (!958). (13) A. J. Hale, The Interference blicroscope, E. and S. Livingstone, Ltd., Edinburgh and Lon- don, 1958. (14) M. Fran•on, Interf•.rences, Diffraction et Polarisation, in S. Fliigge, Encyclopedia of Physics, Springer-Verlag, Berlin, 1956, pp. 171460.

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