FIELDS W, X, and Y 

 Columns 68; 69 and 

 70; and 71 



those particular punches is so improbable; their use in Field Y is only to qualify the evaluation coding 

 they accompany. 



The Log-Probit Grid is an adjunct to Fields X and Y, used, in the case of appropriate data, for 

 determining values for Field Y with Criteria of the 5- series (51, 52, 53, 54, 55, 57, 58, and 59). Its 

 structure is described in Division 24. 



General Use 



This area of the Code is for expressing an evaluation of the intensity of the activity coded in 

 Fields T- 1 and T-2 (i. e. , the relative ability of the test compound for causing the biological response). 

 The primary need for such a coding area is to provide a way of distinguishing, by code, between 

 instances when a test compound produced the response coded in Field T and instances when the 

 compound did not produce the response for which it was tested. Without this basic distinction, the 

 coding of Fields A through V would be merely a description of the test procedure to determine the test 

 compound's ability to cause the response coded in Field T, with no way of indicating whether or not 

 the response actually occurred. 



Beyond the basic need for distinguishing between production of a response ("positive activity") 

 and failure to produce a specific response ("negative activity"), the CBCC has established means of 

 coding grades of positive activity. Certain consistency has been achieved by the CBCC's assuming a 

 leveling policy of "non-interpretation", in other words, a policy of coding, to the extent possible, only 

 the evaluation of the positive response as the author expressed that positive evaluation. To this end, 

 Field X has been provided with the common criteria, as well as some of the more special criteria, used 

 by authors for evaluating positive results of their tests. (No way has been conceived for reducing 

 positive results from tests of all types so that they might all be evaluated by a single common criterion. ) 

 Field Y is used to code the actual evaluation (inactivity and levels of activity), based on whatever 

 criterion is coded in Field X. 



In addition to the importance of coding the evaluation in order to achieve a complete code 

 statement of each individual test, the evaluation coding is of prime importance to the original concepts 

 and objectives of the CBCC, the correlation of chemical structures and biological responses to those 

 structures. This correlation is conceived as leading to predictions of undetermined biological responses 

 either to a given known chemical or to chemicals of a given structural type and to suggestion of direction 

 of synthesis for new compounds for specific biological actions. In order to make possible the assembly 

 of coded information significant to such correlation and prediction, it is essential that the results of 

 biological tests (i. e. , evaluation ) of known chemicals be coded , thereby rendering this information 

 capable of being mechanically sorted. Studies of this nature would typically be concerned with the 

 coded evaluations of all biological responses known for which a given chemical was tested or for which 

 chemicals of a given structural type were tested; on the other hand, such studies might revolve about a 

 given biological activity, in which case all compounds known to have been tested for that activity 

 would be assembled to determine if the active (or inactive) chemicals had structural characteristics or 

 physical properties in common. 



With this concept in mind, consideration was given to providing a means of recording as pre- 

 cisely as possible the basic capacity of test compounds to cause biological responses. For purposes 

 of explanation, attention is called to the basic coding of "positive" activity (i. e. , when the biological 

 response in Field T occurred) vs. "negative" activity (i. e. , when the biological response in Field T 

 did not occur), ignoring the problem of coding of the degree of positive response; if consideration is 

 restricted to this simple aspect, it may be more easily understood what is meant by the basic ability 

 of a compound to cause a biological response. Fields X and Y make the distinction between positive 

 activity and negative activity as it was demonstrated under conditions of the test; negative activity is 

 always indicated by one of three criteria in Field X (01, 02, or 62) with Symbol 1 in Field Y; any other 

 coding in Fields X and Y represents positive activity. At first consideration, it might seem adequate 

 to consider that whenever a compound fails to cause a given biological response (coded as negative 

 data) in a given test, it is thereby demonstrated to be Incapable of causing the response. Unfortunately, 

 another factor plays a role at the "activity-inactivity" level which, for any given test, is too important 

 to ignore, the quantity of the test compound to which the biological system was exposed in the test 

 being coded. Fields X and Y can code only the response to whatever amount of chemical was administered. 



172 



