ULTRASOFT X-RAY MICROSCOPY 



crophotometer tracing of an individual cell. 

 Using the relation {12) the mass thicl<;ness, 

 m, was calculated for each radial position 

 and the total mass was obtained from these 

 values b}^ a nimierical integration (using 

 Simpson's rule). Each experimental point is 

 of equal effect in the calculation for total 

 mass because these were taken at radial posi- 

 tion of equal steps in the T^^-value. {R the 

 radial position) as shown by the relation for 

 total mass, M 



M 



2irRm{R) dR 



Jo 



7rm d{R^) {16) 



A digital computer Avas programmed to do 

 this numerical integration so as to allow a 

 large number of cells to be measured viz. 800. 

 The average cell mass for the particular sam- 

 ple used in this study was found to be 29.7 X 

 jO-12 gram. Twenty-five independent meas- 

 urements were taken on one typical cell in 

 order to determine a precision measure. For 

 this cell, the yiim value was 45.8 and the 

 average deviation was 1.78 or about 2.6% 

 which is consistent with that predicted above 

 from {15). This corresponds to a precision 

 of about 1 micro-microgram for this cell 

 measurement. 



With such precision, it was possible to pre- 

 sent the 800 single-cell measurements as a 

 histogram in order to indicate the manner 

 with which the cell mass is distributed about 

 an average value. This single cell mass distri- 

 bution curve is shown in Fig. 20. This distri- 

 bution is presented in mass units m relative 

 to average mass in and was based directly 

 upon the yum data so it is independent of the 

 accuracy of measurement of both 7 and the 

 mass absorption coefficient, /x. 



REFERENCES 



1. a. "Principles of Microradiography and Bib- 



liography," prepared by the Eastman Ko- 

 dak Research Laboratory and Published by 

 the Philips Electronics Corporation, Mt. 

 Vernon, N. Y. 



b. George L. Clark, "Applied X-Rays," 

 McGraw-Hill, N. Y., Chapter 10, 1955. 



c. "X-Ray Microscopy and Microradiogra- 

 phy," Academic Press, N. Y., 1957. 



d. A. Engstrom, "Historadiography," Physi- 

 cal Techniques in Biological Research, Aca- 

 demic Press, N. Y., Vol. Ill, 1956. 



e. LiNDSTROM, B., (Thesis), Acta Radiol., Supp. 

 125, 1955. 



f. Ong Sing Poen, "Microprojection with 

 X-Rays," Martinus Nijhoff, The Hague, 

 1959. 



g. Henke, B. L., "Microstructure, Mass and 

 Chemical Analysis with 8 to 44 A X-Radia- 

 tions," Proceedings of the Seventh Annual 

 Conference on Industrial Applications of 

 X-Ray Analysis, University of Denver, 

 1958. 



2. Ong Sing Poen and Le Poole, J. B., Applied 



Scientific Research B7, 265 (1958) . 



3. Nixon, W. C, Proc. Rorj. Soc. A232, 475 



(1955). 



4. Henke, B. L. and Miller, J. C, Technical 



Report— AFOSR TN 59-895. 



5. Henke, B. L., White, R., and Lundberg, B., 



J. Appl. Phijs. 28, 98 (1957). 



6. Feldman, C. and O'Hara, M., J. Opt. Soc. 



Am., 47, 300 (1957). 



7. Pattee, H. H., Science, 128, 977 (1958). 



8. See also Schaefert, R. N. and Oughton, C. 



D., /. Opt. Soc. Am. 38, 991 (1948). 



9. Henke, B. L. and Ong Sing Poen (in prepara- 



tion) . 

 10. Henke, B. L. and Maley, C. (in preparation). 



Burton L. Henke 



VASCULAR AND DENTAL APPLICATIONS OF 

 PROJECTION MICROSCOPY. See MICRO- 

 ANGIOGRAPHY, p. 627. 



693 



