THE REPRODUCTION OF VIRUS PROTEINS 12 



By W. M. Stanley 



Department of Animal and Plant Pathology of The Rockefeller Institute for Medical 

 Research, Princeton, N. J. 



Protoplasm is the stuff of life. It has, for some time, been regarded 

 as living matter in its simplest form. It has interested biologists for 

 over 100 years, and has been the subject of extensive physical and 

 chemical studies. However, the present state of our knowledge of 

 protoplasm is best attested to by the fact that we are gathered here 

 in a symposium on the very nature of this material. We know 

 much about protoplasm, yet we do not know what it really is. There 

 is a vital difference between the grayish, translucent, slimy proto- 

 plasm which is the slime molds and the grayish, slimy material of 

 certain protein gels, yet we do not know exactly what constitutes 

 this vital difference. Biologists have, for many years, attempted to 

 differentiate between the living and the nonliving in protoplasm, 

 without much success. According to Seifriz, many of the older ideas 

 have been discarded and the discussion has settled down to the 

 question as to whether a vital substance is concerned or whether proto- 

 plasm results from a certain combination of substances, themselves 

 nonliving. Most of the workers appear to feel that life results from 

 a certain combination of a number of constituent parts, but that if a 

 single vital substance is essential it is probably a protein or protein 

 complex. Since viruses have long been considered to be living 

 organisms and since certain typical viruses have been isolated recently 

 in the form of high molecular weight proteins, it is obvious that a 

 careful consideration of the nature of these virus proteins may throw 

 some light on this question. 



Viruses are of unusual interest in this connection, because with 

 respect to size they bridge the gap between the living and the non- 

 living. At the upper end of a scale (see fig. 1) which includes entities 

 ranging in size from the molecule of egg albumin, through viruses, up 



1 Read at a symposium of the American Society of Naturalists in joint session with the American Society 

 of Zoologists, the Botanical Society of America, and the Genetics Society of America. The American 

 Association for the Advancement of Science, Indianapolis, Ind., December 30, 1937. Reprinted by per- 

 mission from The American Naturalist, vol. 72, No. 739, March-April 1938. 



1 The writer wishes to thank the many individuals who have contributed to the development and 

 clarification of several of the points discussed in this paper. 



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