THE STRUCTURE OF VIRUSES^ 



By W. M. STANLEY 



DEPARTMENT OF ANIMAL AND PLANT PATHOLOGY, THE ROCKEFELLER INSTITUTE 

 FOR MEDICAL RESEARCH, PRINCETON, N. J. 



The atomic theory of matter, the germ 

 theory of disease, and the cell theory of 

 life may appear at first to be quite diverse 

 and unrelated. However, it will be my 

 purpose not only to present the recent ad- 

 vances in virus research, but also to indi- 

 cate that the successful continuation of 

 this work may be dependent upon an in- 

 timate knowledge of the three theories just 

 mentioned and even, perhaps, upon their 

 integration into a new and unified philos- 

 ophy. The atomic theory, which was prob- 

 ably first stated before 1000 B.C., has been 

 subjected to continual modification in detail 

 as a more exact knowledge of atomic struc- 

 ture has been gained, yet the original and 

 basic concept of matter as a discontinuous 

 rather than as a continuous or homogeneous 

 phase has remained unaltered. The germ 

 and cell theories have been subjected to less 

 modification than has the atomic theory, 

 perhaps because of their more recent 

 origin ; with time and new knowledge, it 

 would not be unexpected if they too should 

 require further alteration. It is an un- 

 fortunate fact that knowledge gained be- 

 fore its due time frequently results in a 

 strong desire to overthrow useful theories, 

 and it is only later, following understand- 

 ing, that reconciliation and accord are 

 achieved. For example, it is known that 

 many present-day facts are entirely incon- 

 sistent with the atomic theory as stated by 

 Dalton in 1808, yet the evolution of the 

 theory has been such as to account for 

 these facts and to provide today a valid and 

 coherent atomic theory. The newer know- 

 ledge of viruses may appear inconsistent 

 with present-day theories, yet there is every 

 reason to believe that a more complete 

 understanding of the structure or architec- 



1 This lecture was adapted from an article by 

 the writer which was published with an extensive 

 bibliography in Physiological Reviews^ 19 : 524 

 (1939). 



ture of viruses will permit the blending of 

 hypotheses and facts into a unified phi- 

 losophy without the overthrow of time- 

 honored theories. 



The word "virus" was originally used 

 only in the singular and meant a poison 

 such as a snake venom. Later it was used 

 to denote infectious disease-producing enti- 

 ties without regard to their nature, and 

 more recently it has been applied only to 

 those infectious agents capable of passing 

 through filters that retain ordinary bac- 

 teria. Todaj^, properties ascribed to viruses 

 include not only their ability to pass 

 through fine membranes but also a set of 

 general properties which emphasize the in- 

 timate relationship that exists between 

 viruses and their host cells. Among these 

 properties is the fact that viruses repro- 

 duce, but only within certain living cells; 

 the fact that during reproduction they may 

 change or mutate ; the fact that many virus- 

 infected cells contain inclusion bodies; and 

 the fact that most virus diseases (but not 

 all) are followed by a lasting immunity in 

 recovered hosts. Tobacco mosaic, the first 

 virus discovered, was shown to be filterable 

 by Iwanowski only 47 years ago and was 

 recognized as a new kind of infectious 

 agent by Beijerinck 41 years ago. Other 

 viruses which have been recognized since 

 then include those responsible for the foot- 

 and-mouth disease of cattle, louping ill of 

 sheep, hog cholera, rabies, dog distemper, 

 fowl pox, smallpox, psittacosis, yellow 

 fever, St. Louis encephalitis, horse encepha- 

 litis, poliomyelitis, fever blisters, certain 

 types of tumorous growths in fowls and 

 other animals, various yellows and mosaic 

 diseases of plants, and even for the produc- 

 tion of unusual colors in the flowers of 

 plants, which in tulips is called tulip break. 

 Still more viruses are being discovered 

 from time to time. 



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