W. M. STANLEY 



proved to arise de novo — they are always first found in cells. Viewed in 

 this light, the diflferences in chemical structure that have been demon- 

 strated to exist between different virus strains, and especially the chang- 

 ing of the chemical structure of a virus in a definite manner by means 

 of known chemical reactions, take on a new and perhaps startling 

 significance. There are many virus diseases in which a symbiotic re- 

 lationship is set up between virus and host. Although the virus 

 enters into and alters the metabolic activity of the cell, the cell survives 

 and continues to divide. The virus is carried continuously within the 

 cells, and in some cases could almost be regarded as a normal com- 

 ponent of the cells because of the lack of obvious damage. In fact, 

 one virus has come to be known as the "healthy potato virus" because 

 it is present in almost all potatoes grown in this country and yet the 

 potato plants appear healthy. It is as if one had introduced; from 

 without, a nucleoprotein which was accepted by the cell as a part of 

 its own germ plasm. The fact that different strains of a virus, which 

 can cause different manifestations of disease, are characterized by 

 different nucleoproteins, and especially the fact that the structure of 

 these nucleoproteins can be changed in the test tube by means of known 

 chemical reactions, could be interpreted to mean that eventually the 

 germ plasm of cells may prove to be susceptible to similar chemical 

 manipulation. The viruses have assuredly provided a link between 

 molecules and organisms, and there now exists a pathway leading from 

 simple structures, such as the electron, to massive, highly complex 

 structures, such as man. This pathway is broad and well established 

 in some places and narrow and difficult to traverse in others. But as 

 the latter are broadened and placed on a firm foundation, through 

 the common effort of chemists and pathologists, it is possible that 

 information will be acquired which could affect the future destiny of 

 every living being in the world. 



Selected References 



Anson, M. L., and Stanley, W. M., J. Gen. Physiol., 24, 679 (1941). 

 Bawden, F. C, Plant Viruses and Virus Diseases. Chronica Botanica, Wal- 



tham, 1943. 

 Beard, J. W., Bryan, W. R., and Wyckoff, R. W. G., J. Infectious Diseases, 65, 43 



(1939). 

 Bernal, J. D., and Fankuchen, I., J. Gen. Physiol, 25, 111, 147 (1941). 



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