Vl PREFACE 



To what extent the field of bioelectrical measurements has been en- 

 riched since the celebrated investigations of du Bois-Raymond, with the 

 aid of vacuum-tube amplification technique coupled to the modern 

 cathode-ray oscillograph, is discussed as the biophysical problem of nerve 

 conduction. 



The final chapter discusses the technical limitations of the optical 

 microscope and points to the electron microscope, with its enormous 

 resolving power, as the instrument which awaits the cooperative interests 

 of experts in the biological sciences as the tool to investigate the struc- 

 ture of organic matter. 



The publishers have generously cooperated by subscribing to the 

 pedagogic axiom that one good illustration equals 1000 printed words. 



The General Electric X-Ray Corporation, the Victoreen Instrument 

 Company, Bausch and Lomb Optical Company, National Carbon Com- 

 pany, Weston Electrical Instrument Corporation, Kipp and Zonen, 

 Fisher Scientific Company, American Standards Association, Central 

 Scientific Company, Allen B. DuMont Laboratories, Eastman Kodak 

 Company, Electro-Medical Laboratory, Inc., and the R. C. A. Research 

 Laboratories have all been generous in supplying many original photo- 

 graphic illustrations, for which I express my appreciation. 



It is a pleasure to thank Dr. S. J. M. Allen for furnishing the new data 

 on x-ray absorption coefficients; Mr. J. L. Weatherwax for the use of 

 his water phantom data; Mrs. E. H. Quimby, of the Memorial Hospital, 

 New York, for clinical data on radiation therapy; Dr. D. B. Lindsley for 

 the original electroencephalograms; and Dr. V. K. Zworykin for the 

 photographs of the electron microscopes. 



I am indebted for many excellent suggestions made by my colleagues 

 in the Medical School. For criticisms of various chapters I am indebted 

 to Professors H. A. Blair, H. D. Crockford, J. F. Dashiell, R. B. Lyddane, 

 A. E. Ruark, and P. E. Shearin. 



O. S. 



Chapel Hill, N. C. 

 January, 1943 



