THE PROBLEMS OF VIROLOGY \) 



knowledge and there will be variations in its application in different fields of 

 science, but in general and at the level of normal laboratory thought, the 

 important principles may be stated as follows: 



1. To determine the conditions under which an observed phenomenon can 

 be reproduced with regularity. 



2. To define the parameters which determine its quantitative expression. 



3. To express its relation to other phenomena in the simplest acceptable 

 form. 



4. On the basis of these results and deductions, to examine whether new 

 phenomena occur as would be expected in other relevant fields. 



In a general treatise, it is conventional and necessary to exclude description 

 of the technical detail needed in every experimental manipulation to ensure 

 reproducibihty of results. Quantitative results will also be limited to an 

 occasional illustrative protocol. With some obvious qualifications, the 

 essential task of a comprehensive treatise is to express in the simplest accept- 

 able terms the relationship between the phenomena observed within the 

 chosen field of study. 



There can be no question that the most acceptable form of simplification 

 is the generalized mathematical expression that, within stated limitations, 

 allows a quantitative statement of the expression of the phenomenon. 

 Even in the most exact of the experimental sciences any statement of this 

 type will need to be qualified by some indication of the range of variability 

 introduced by inadequacies in the technique of observation. In biological 

 phenomena this tends to be so large that there is stiU a grave distrust 

 among experimentalists of attempts to derive a mathematical relationship 

 directly from a set of observations. The other procedure — to derive a working 

 hypothesis from the general pattern of results and to show that the results 

 are not inconsistent with the quantitative implications of the hypothesis — 

 is more usual. Except at a rather superficial level, even this is rarely attempted 

 in virology, where it has not often been possible to isolate systems from dis- 

 turbing environmental and intrinsic circumstances sufiiciently to allow 

 quantitative reproducibility. Even in the reproduction of bacteriophage, 

 individual infected units show a wide range of yield and time of lysis. The 

 destruction of the functional activity of a virus population by such accurately 

 measurable agents as heat, various types of ionizing radiation and, with some 

 qualification, immune serum, is sufficiently regular to allow a satisfactory 

 quantitative formulation. Outside of this special and limited field there has 

 been little success in providing quantitative formulations of virus behavior. 

 Virtually all current work on the process of viral infection is in a sense 

 quantitative, but the characteristic statement of the results is in the form of 

 a scatter diagram sufficiently consistent to indicate a qualitatively significant 

 regularity but quite unsuited for any more refined mathematical handling. 



