8 F. M. BURNET AND W. M. STANLEY 



the position been resolved by the recognition of neuraminidase as an essen- 

 tial component. Here the problem was simplified by two factors: (1) that the 

 substrate of the enzyme has a functional relationship to the entry of the 

 virus particle into its host cell and (2) the absence of any enzyme of similar 

 action in host tissues. Where an enzyme well-known to be present in host 

 tissues is shown to be present in or on conventionally purified virus particles, 

 an almost insoluble problem of interpretation is presented. A good example 

 of this difficulty is discussed in relation to the virus of erythroblastosis by 

 Andervont in Volume III. Kecent work on the attachment of bacterial 

 viruses to their hosts points strongly to the existence of enzymatically active 

 groups at the end of the tail. There are, however, only preliminary indications 

 of the nature of the enzyme(s) or substrate(s) concerned. 



B. The Virus-Host Cell Relationship 



The characters of the infective virus particle represent only a minor part 

 of the significant information to be gained from the laboratory aspects of 

 virology. The interactions of the virus and host cell, which are of the utmost 

 importance insofar as the true expression of viral activity is concerned, are, 

 however, much more difficult to observe and interpret than the physical and 

 chemical qualities of the infective particles. For example, there are viruses 

 which cause cancer in several kinds of animals, yet almost nothing is known 

 concerning the mode by which a virus can urge cells toward wild and mi- 

 organized growth. This problem and its possible relationship to the human 

 cancer problem have been discussed by one of us (Stanley, 1957, 1958). The 

 difficulties are common to all aspects of intracellular function and, in fact, 

 provide an important area of controversy in regard to the objectives of bio- 

 logical investigation and the form and legitimacy of generalization. In most 

 technical publications in virology it is sufficient to conform to the accepted 

 canons of scientific investigation without expressed question as to the basis 

 of the conventional approach. It seems to us, however, that in a general 

 treatise some attempt should be made to discuss somewhere not specific 

 interpretations and hypotheses but the type of ideas in terms of which 

 general statements may appropriately be made. This demands a brief dis- 

 cussion of the objectives of scientific work in the biological field. 



In general, biological research has two immediate motivations. Usually in 

 the backgroimd, but sometimes dominant, is the objective of providing ways 

 by which felt and expressed human needs may be satisfied. The more im- 

 portant motivation of scientific work can perhaps be expressed as to exper- 

 ience the various emotional and intellectual satisfactions and social rewards of 

 effective work within the accepted canons of scientific investigation. As a result 

 of three centuries of modern science, a body of experimental and logical 

 procedures has been developed. This will inevitably change with increasing 



