ELECTRON MICROSCOPE IN BIOLOGY — WYCKOFF 257 



The particles of several other viruses, including bacteriophages, 

 are derived from the protoplasm of the host cells ; but there are other 

 viruses that do not have such an origin. Some appear to arise from 

 specialized components of the diseased cell, whereas others may be 

 foreign invaders that multiply like micro-organisms, by growth and 

 division. Much more observation is needed before the full story of 

 virus growth is known; but it is important that we at last have a 

 method capable of giving this knowledge. 



At this early stage in our explorations with the electron microscope 

 it is not possible to foresee what new insights into the vital process 

 it will next give us. Perhaps they will come as we address ourselves 

 more and more toward the small viruses, especially those that attack 

 nervous tissue; or perhaps we shall find more immediately rewarding 

 the closer study of the numerous structures that are steadily being 

 found as we examine a widening range of healthy cells. Wliichever 

 it is, we may be sure that our visual penetration of the macromolecular 

 level of organization will prove steadily more fruitful as experience 

 gives us an increasing ability to interpret the new tilings we observe. 



Reprints of the various articles in this Report may be obtained, as 

 long as the supply lasts, on request addressed to the Editorial and Pub- 

 lications Division, Smithsonian Institution, Washington 25, D. C. 



