14 THE PHYSICS OF VIRUSES 



pure preparations, and has been exploited to some extent. The 

 rewards are size and shape figures and, occasionally, internal 

 structures. 



In addition to these, the two features possessed by viruses — 

 large size on the molecular scale, and sensitivity of biological 

 properties — enal)le sedimentation studies in centrifugal fields 

 and diffusion studies to be made, and thermal and jn-essure 

 effects to be measured. 



Now, none of these alone can be taken as finally informative, 

 because the essential character of work in the unseen submicro- 

 scopic world is that it is inferential. Therefore, as in modern 

 physics, we must wait for agreement between several lines of 

 work before stating firm conclusions. This is already l)eginning 

 to happen. For example, the size and hydration of southern 

 bean mosaic virus, determined by sedimentation and diffusion, 

 agrees quite well with measurements made in the electron 

 microscope and by small-angle X-ray scattering. The electron 

 microscope data are further checked by deuteron bombardment 

 studies. So the interplay of varied information, which has l)uilt 

 atomic physics wholly in the unseen world, is beginning to 

 take effect in the physical studies of viruses. The function of 

 this book is to show where these studies are leading us, and to 

 what extent the physical method has i)ower. 



References 



Smith, K. M.. An Introduction to the Study of Viruses. Blakiston. Philadel- 

 phia (1951). An excellent, simple general account. 



Rivers, T. M.. Viral and Rickettsial Diseases of Man (J. B. Lippincott Co., 

 New York, 1948). Contains valuable articles on viruses in general, on tech- 

 nique, and on many pathogenic viruses. 



Bawden. F. C, "Plant Viruses and Virus Diseases," Chronica Bntan. 23 (1950). 



A very complete and interesting account by an author wlio is thoroughly 

 saturated with plant virus knowledge. 



Delbriick. M., Viruses 1950 (California Institute of Technology, Pasadena, 

 Calif., 1950). A very interesting and authoritative series of articles with a 

 compact and valuable syllabus of bacteriophage knowledge. 



Lwoff, A., "Lysogenic Bacteria" Endeavour 11, 7'-2. 13''2 (195'2). Two compact 

 and readable articles on this subject. 



Knight, C. A., J. Biol. Chem. 171, 297 (1947). 



Stanley, W. M. and Lauffer, M. A., in Viral and Rickettsial Disease of Man 

 (1948). 



